Ube White Chocolate Ganache Tart

Purple sweet potato gives this ganache tart delicious flavor and a naturally purple hue. Classic French shortcrust pastry is the perfect foil for the rich filling.

Spring is yet to come, but flower-shaped tarts are already blooming in my kitchen! I’ve been gathering a few new baking tools lately and donating old ones, which feels good on the precipice of the new season. You may recall that I recently purchased a new madeleine pan (see here) and using it inspired me and gave my baking a boost! Around the same time I purchased this blossom tart pan, and I’ve just been waiting for the right inspiration to use it.

This year I’m making an effort to explore ingredients that give foods a naturally vibrant hue. Purple yam, known as ube (pronounced ooh-bae), is one of those ingredients that imparts bold purple color naturally – and it doesn’t just look good! It tastes good too, with beautiful sweet potato flavor.

Since fresh ube is nowhere to be found in the US, and fresh purple sweet potato isn’t stocked at my neighborhood grocery store, and I’m not inclined to go looking around for it under current circumstances, I did the next best thing. I ordered some purple sweet potato powder online. 

You can find it right here.

I’m well acquainted with other food powders often used in pastry, such as freeze dried powdered fruit and matcha green tea. But purple sweet potato powder was new to me, and I suspected it would be quite starchy. I took a leap of faith and added a good portion to some hot heavy cream for ganache, and it diluted rather well. I did get out the immersion blender for insurance that things were well-mixed. It was really neat watching the cream turn purple while mixing.

After a taste-test, I decided the potato flavor needed to be a little more pronounced, so I reconstituted more of the powder with hot water. I shouldn’t have been surprised when the mixture practically turned into purple mashed potatoes! I added them to the cream a little at a time until a pronounced potato flavor was achieved, and I really love the end result.

After the cream was well mixed and still hot, I added chopped white chocolate (these Baker’s bars) and the whole mixture turned into the most beautiful purple sweet potato ganache. 

You’ll have some ganache left over after filling a 9-inch tart pan – and guess what!? – it whips!

I chilled the ganache then whipped it to stiff consistency on the stand mixer, then transferred the mixture to piping bags. I piped stars and kisses using a star piping tip and a plain 1/2-inch piping tip. The stars I used on the tart, and we ate the kisses like truffles!

My favorite pastry crust is pate sucree, and it was so perfect for this tart. Save the crust remnants for cookies – they are so nice all on their own. Cut into flower shapes they are just so cute for a tart decoration.

The filling is deliciously rich, and needs a little hit of acidity. Fresh raspberries work well for this, but you could also use blueberries, strawberries or pomegranate arils.

The petal tart pan I used can be purchased at Pastry Chef Central, here

Although ube and purple sweet potato are not exactly the same thing, they are very close – close enough for me to use the words interchangeably. There is a small difference in flavor, but they are both relatives of the orange sweet potato (and the flavor will remind you of its origin). For more information about their differences, see this informative page.

What a delightfully fun and tasty tart this was to make! We usually have southern-style sweet potato casserole for Easter dinner (is that just a southern thing, or do other people eat sweet potatoes for Easter?) but I may have to swap this in. It’s more likely that I’ll just make both.

Ube White Chocolate Ganache Tart

Heather Baird
Purple sweet potato gives this ganache tart delicious flavor and a naturally purple hue. Classic French short crust pastry is the perfect foil for the rich filling.
I made this in a 9-inch blossom-shaped tart pan with a removable bottom, but you could use a standard 9-inch pie plate or an 11-inch standard-sized tart pan.
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Prep Time 35 mins
Cook Time 25 mins
4 hours chill time 4 hrs
Total Time 5 hrs
Course Dessert
Cuisine American
Servings 10

Equipment

  • tart pan

Ingredients
  

Pate sucrée crust

  • 2 cups 10oz/245g all-purpose flour
  • Pinch of salt
  • 7/8 cup 14 tablespoons/198g unsalted butter, cold and cubed
  • 1/2 cup 3.5 oz./100g fine granulated sugar
  • 1/2 teaspoon vanilla extract
  • 1 egg slightly beaten

Ube Filling

  • 1 1/2 cups heavy whipping cream
  • 6 tablespoons ube or purple sweet potato powder
  • Hot water
  • 12 oz. three 4oz. bars white chocolate, chopped

Assembly

  • Frozen ube ganache stars
  • Pate sucrée cookies
  • 4 oz. fresh raspberries
  • 1/2 tablespoon poppyseed
  • Organic rose petals optional

Instructions
 

Tart dough

  • Place the flour, salt, and sugar in the bowl of a food processor, pulse to combine. Add the cubed butter on top of the flour and pulse repeatedly in short bursts until the mixture looks crumbly. Add the vanilla and egg and pulse until the mixture forms a ball to one side of the bowl. Remove the dough and flatten into a circle. Cover with plastic wrap and let rest 30 minutes before use.
  • Preheat the oven to 375°F.
  • Roll the dough on a lightly floured piece of parchment paper using a floured rolling pin to 1/4-inch thickness. Pick up the pastry on the paper and invert it onto the tart pan or pie plate. Peel away the parchment and fit the crust into the pan. Trim away the excess dough. Chill the crust in the pan for 15 minutes.
  • Fit a piece of parchment on top of the pie crust and add pie weights (I use dry brown rice). Cook for 20-25 minutes, or until the pie is golden around the edges and fragrant. Let cool completely.
  • Re-roll dough scraps to 1/4-inch thickness and cut out various sizes of flower shapes. Transfer to a parchment-lined baking sheet and bake for 10-12 minutes, or until cookies are golden. Let cool completely.

Ganache

  • Heat the cream in a saucepan over medium heat until steaming but not boiling. Add 3 tablespoons of the ube powder; whisk until well combined. In a separate bowl, place the remaining 3 tablespoons of ube powder. Add hot water a little at a time as needed (about 3-4 tablespoons at first, then more to consistency) to form a medium-bodied potato paste. Whisk this mixture into the cream a spoonful at a time. If the mixture looks lumpy, use and immersion blender to combine it thoroughly (or transfer to a blender, but be careful not to turn the heavy cream into whipped cream). While the cream is still hot, add the white chocolate and whisk gently to combine. When a glossy ganache is formed, pour it into the cooled pie crust. You will have leftover ganache. Transfer the pie to the refrigerator to chill 4 hours, or overnight.
  • Chill the leftover ganache for at least an hour or until the bowl is cool to the touch. Whip the ganache on a standing mixer on high speed until a thick, buttercream-stiff consistency is achieved. This will cause the purple hue to lighten.
  • Line a baking sheet with parchment. Transfer the whipped ganache to a piping bag fitted with a large open star tip. Pipe large and small stars on the parchment paper and transfer to the freezer to set firmly, about 30 minutes.

Assemble

  • When the tart is firmly set, use a small offset spatula to pick up frozen ganache stars from the parchment and transfer to the top edge of the tart. Alternately place cookies, raspberries and rose petals, if using. You can cover one side of the tart with decoration as I did, or completely fill the center of the tart. You should have enough cookies and ganache stars to do so. Serve the tart immediately, or cover and chill until you’re ready to serve. Refrigerate leftovers.
Keyword purple sweet potato, rosemary ice cubes
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Anonymous
Anonymous
6 months ago

Yum! I tried plain purple sweet potato pie for T-day, to fam acclaim! What a great idea to add white choco!

Heather Baird
Heather Baird
6 months ago
Reply to  Anonymous

That sounds delish!

Unknown
Unknown
6 months ago

If you're looking for natural ingredients that add vibrant color, you have to try butterfly pea tea! It's a striking blue on its own and turns magenta when it comes into contact with an acid. It's quite fascinating!

Heather Baird
Heather Baird
6 months ago
Reply to  Unknown

Thank you for the recommendation! I have a bag but haven't opened it yet. I'm excited to try it!

Indya | The Small Adventurer
Indya | The Small Adventurer
6 months ago

This looks amazing! I cannot get over the incredible vibrant purple ?