Over no heat, combine the brown sugar, cornstarch, and salt in a medium saucepan. Whisk in the egg yolks, and slowly whisk in the milk and cream.
Turn the heat to medium-low, and whisk continuously until the mixture thickens and comes to a simmer. This will take several minutes.
When the mixture is thick enough to stay on the whisk, stir in the butter and vanilla. Whisk until combined and turn off heat.
Transfer mixture to a bowl and cover with plastic wrap, making sure to press the plastic onto the entire surface of the pudding.
Chill until ready to fill the doughnuts — at this point, you’ll add mashed banana to the cream. Use the whole banana for all of the cream, or divide the pudding in half and add half the banana to it.
Put the yeast, warm water, and a pinch of sugar in a small bowl. Stir and let sit for about 5 minutes until foamy.
In the bowl of a stand mixer fitted with a dough hook, add 3 cups of flour, milk, butter, egg yolks, sugar, salt, and cinnamon.
Turn the mixer to medium-low and mix until a soft dough forms. Increase the speed to medium-high and mix for 3-4 more minutes. Your dough will be slightly sticky but should clear the sides of the bowl. If it doesn’t, add more flour 1/4 cup at a time, but try not to add more than about 1/2 cup, as the dough should be sticky.
When done mixing, remove the bowl and sprinkle the dough very lightly with flour.
Cover with a towel and let the dough rise at room temperature (choose the warmest spot in your kitchen) for about 2 hours until the dough has doubled in size.
After the dough has risen, turn it on a lightly floured surface. Roll the dough into a 12-inch rectangle. Using a 3-inch round cookie or biscuit cutter, cut 12 rounds out of the dough and transfer to a baking sheet. You can re-roll the dough and cut out more doughnuts, but be aware that they will be much tougher and not as good. Cover with a towel and let rise for 30 minutes.
While the dough is rising, get a 4-5 quart pot and fill about 3 inches with vegetable oil. If you have a deep fryer, that will work here as well. Heat the oil until it reaches 350 degrees on a deep-fry thermometer.
After the doughnuts have risen for a second time, fry each one until golden brown, flipping with a slotted spoon or skimmer.
Remove from oil and put cool on a wire rack. Continue until all doughnuts have been fried.
Preheat oven to 350 degrees F.
Combine all of the ingredients in a mixing bowl. Mix until combined — it should be kind of clumpy.
Spread on a baking sheet and bake for 15 minutes. Let cool until ready to use.
Put the cream, sugar, vanilla, and a pinch of salt in the bowl of a stand mixer fitted with a whisk attachment (Note: you can use a hand mixer or even a whisk for this) and beat on high until thick and creamy.
Make the ganache just before you are ready to glaze your doughnuts
Put the chocolate in a heat-proof mixing bowl.
Heat the cream in a small saucepan over medium-low heat until it comes to a simmer. Do not let it boil.
Pour the hot cream over the chocolate. Let sit for 5 minutes and then stir with a rubber spatula until smooth.
To put the doughnuts together:
Make sure your doughnuts are at room temperature before filling.
Insert the back of a spoon or a chopstick into the doughnuts.
Fit a piping bag with the widest tip you have. Fill the bag with pudding — either vanilla or banana — and pipe into the doughnuts. This will be messy, and you’ll probably think you’re doing it wrong, but it is what it is.
For the whipped cream, you can use a pastry bag and pipe it on top or just use a spoon.
Sprinkle with the graham crumbs and banana slices if desired.
For the ganache, fill your doughnuts, make the ganache, and then glaze the doughnuts with ganache. Immediately sprinkle with graham crumbs.
Storing leftovers: Leftovers can be stored in an airtight container either at room temperature or in the fridge but should be eaten as soon as possible.Variations: Fill with any variety of cream — chocolate, butterscotch, coconut. Can use vanilla wafers instead of graham crumbs, and milk or white chocolate ganache. You can also skip the fillings and roll the doughnuts in cinnamon or powdered sugar.Pairs well with:Chocolate Chai Cold Brew, Earl Grey Lavender Latte