Gel food colors: redburgundy, yellow, chestnut brown
1/2cupready-made buttercream tinted golden yellow
Prepare six 3×6-inch aluminum molds as outlined in the tutorial in this blog post.
Make the cakes: In a large bowl, sift together the flour, baking powder, and salt. Heat the milk and butter in a small saucepan over low heat until melted. Set aside.
Separate the egg yolks from the egg whites. Place the egg whites in the bowl of an electric mixer fitted with the whip attachment. Beat on high speed until foamy, then gradually add half of the sugar (6 tbsp.) and the cream of tartar. Beat to soft peaks. Remove whites to a large bowl.
Place the egg yolks in the standing mixer bowl that the whites were beaten in (do not wash bowl) and beat in the remaining sugar (6 tbsp.) Beat on high speed for 5 minutes with a timer set, or until the yolks are pale yellow and thick. Pour the egg whites over the yolks, and then add the flour mixture. Beat on low speed for a few seconds until just combined. Add the reserved melted butter and milk mixture and fold together briefly until no streaks of egg whites remain.
Spoon or pipe batter into the molds, filling each about 3/4 full. Bake until the cake tops are golden and feel firm when touched, 20-23 minutes. Let cool and remove from molds by gently unwrapping the aluminum foil. Transfer to wire racks to cool completely.
Make the franks: Knead the covering chocolate until smooth. Use gel food colors and gloved hands to knead color into the chocolate. I found the perfect hue by mixing together red and burgundy, with just a touch of golden yellow and chestnut brown. Divide the tinted chocolate into 2-ounce portions and roll under your palms into a 5 inch frank shape.
Lightly brush the top golden portions of the sponge cake buns with piping gel. If you don’t have piping gel on hand, use honey or even a tiny bit of corn syrup. Sprinkle on poppy seeds for a fun, authentic Chicago-style bun appearance. (You could also sprinkle on toasted sesame seeds or just leave the buns plain.) Use a large serrated knife to split the sponge cake down the center lengthwise. Use sawing motions as you cut to avoid flattening the cake. Place a chocolate frank into each bun. Transfer yellow buttercream to a disposable piping bag with a small hole snipped in the end. Pipe a squiggle of icing down the center to mimic mustard.
Allow the cakes to stand until the buttercream sets, about 5 minutes. Package in cute hot dog wrappers (as shown) or place on a serving tray and cover with plastic wrap.
Keyword april fool's food, homemade twinkie, mini sponge cakes