Generously butter two 10x15 jelly-roll pans. If you don't have this size pan you may use sizes larger than 10x15. I would not suggest using sizes smaller than 10x15. Place both the pans on two cooling racks.
Turn stove-eye or burner to medium heat.
In a large saucepan combine the corn syrup, 1 cup of the heavy cream, sugar and pinch of salt. Stir well.
Set pan over heat and stir constantly until the mixture comes to a bubble. This will take about 10-12 minutes. Mixture will appear milky at first, then as it heats it will slightly lose its opaqueness.
When mixture boils, very slowly add the remaining heavy cream stirring constantly- be careful not to disrupt the boil. Lower the heat to medium-low. Set a timer for 6 minutes and allow mixture to bubble. It will rise high and bubble quite a bit during this 6 minute stage.
When time is up, add butter 2-3 cubes at a time and mix until butter has melted. Repeat with remaining butter cubes.
Insert candy thermometer and let mixture bubble until it reaches 250 degrees. When you first insert the thermometer, the temperature will be around 200-217 degrees. It will take a good 30-40 minutes for the mixture to reach 250. Do not rush this phase by turning up the heat. It is within this time frame that the caramel takes on its amber color.
When 250 is reached, remove pan from heat-source and pour half of the caramel in one pan and half in the other. Allow caramel to cool to room temperature. While you're waiting for the caramel to cool, make the creme filling.
In the bowl of a stand mixer fitted with the paddle attachment, cream together sugar,shortening and vanilla. The mixture will be dry and crumbly and you'll probably wonder if you've done something wrong. Nope! You're on the right track. Stop the mixer and scrape down the edges several times.
Place 1/4 cup water in a small bowl and sprinkle the gelatin over. Let stand until absorbed.
Microwave gelatin for 10 seconds or until clear and liquid. Add to the bowl of the running mixer.
The mixture will soften and become thick and doughy. Mix the heck out of it until it starts climbing the sides of the bowl. Scrape down the sides (and bottom, especially if using a Kitchen Aid) and mix again.
Place a portion of the dough in a disposable pastry bag or zip-top bag with the corner snipped. Make sure the hole is big enough to pipe a nice thick line of creme filling - at least 1/4". Set aside.
Cover remaining creme filling with a damp towel so it doesn't dry out.
Lay out several sheets of parchment or wax paper on a work surface - preferably a large cutting board or a surface you don't mind cutting on.
Remove caramel from one of the pans. It should remove easily if you lift one corner and peel the entire slab of caramel away from the buttered pan. Place it on the paper-covered work surface.
Cover caramel with additional wax paper and roll it a little thinner with a rolling pin. Try to achieve an even thickness.
Remove paper and cut caramel into long strips, about 2-2 1/2-inches wide. Pipe a line of creme filling down one side of the length of the caramel.
Roll creme filling into the caramel. The caramel will fold over easily and overlap. Roll and gently stretch into a 16" length. Cut in two 8" pieces. Tip: The caramel rope will squeeze together when you cut it, making the ends flat. You can either squeeze it back the other way to make a round end, or refrigerate the lengths for a few minutes before cutting. The cold ropes will snap off evenly at the ends when cut with a sharp knife.
Repeat with remaining caramel and creme. This will take some time, as there is a lot of candy to work with.
Roll the candy in powdered sugar and dust off excess. Wrap each candy in a layer of plastic wrap, then in a wax paper length with the ends twisted. This helps the candies keep thier shape.
Alternatively, you may choose to lightly brush one end of the candy with water until tacky, then dip in chocolate jimmies or sprinkles. (I much prefer the powdered sugar.)