Use a vegetable peeler to make small curls from the chocolate bar, collecting them in a medium bowl. Be careful not to handle them too much, as they can melt very easily. Set aside.
Place the chopped chocolate in a medium heat-safe bowl. Transfer the cream to a medium pot and bring to a simmer over medium heat.
Pour the hot cream over the chopped chocolate and let sit for 1 minute. Stir the ganache to combine, then let sit, uncovered, at room temperature while you make the doughnuts.
Make the doughnuts: Heat 3 to 4 inches of oil over medium-high heat until it reads around 350°F on a thermometer (or throw a scrap piece of dough in as a tester—if the dough bubbles and rises to the surface, the oil is good to go).
While the oil heats, roll out the doughnut dough on a lightly floured surface to 1/2 inch thick. Use a circle cookie cutter (I like 2 1/2 to 3 inches in diameter) to cut rounds of dough. Alternatively, you can cut the dough into sqaures (about 3x3 inches).
Let the doughnuts rise, covered, on a lightly floured surface for 30 minutes to 1 hour. When the oil is hot, gently add the doughnuts to the pot in batches, frying until they’re golden brown on both sides, 3 to 4 minutes.
Drain the doughnuts on several layers of absorbent paper towels. Let cool for 5 to 10 minutes before filling and glazing.
While the doughnuts cool, transfer the jam to a pastry bag with a medium circle tip. Use the handle of a wooden spoon to poke a large hole in the side or base of the doughnuts.
Place the pastry tip in the hole on the doughnut, and apply pressure to the bag. Fill the doughnut until it feels a bit heavy, like there’s plenty of filling inside.
Dunk the filled doughnut into the chocolate glaze, then into the chocolate curls. Serve immediately.
I always carry three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's pie. My first cookbook, The Fearless Baker, is out on October 24, 2017.