Make Pastry Cream

1. Bring half & half to a simmer on medium heat in a medium saucepan
2. Whisk together sugar, eggs and flour in a separate medium bowl until ingredients are well incorporated. Then slowly whisk hot half & half into the egg mixture. Transfer back to the saucepan on medium heat, whisk mixture constantly until thickened, about 5 minutes
3. Pour into a medium bowl and stir in vanilla. Press plastic wrap onto the surface of the pastry cream. Cover and chill until cold, about 4 hours. (This can be made 1 day ahead of time and kept in the refrigerator)

Thin Pastry Cream for Piping

1. In an electric mixer, whip heavy cream on high speed to soft/medium peaks and transfer to a bowl
2. Beat the chilled pastry cream on medium speed until smooth and soft enough to fold in the whipped cream, about 1 minute
3. Fold whipped cream into the pastry cream. Cover again with plastic wrap pressed against the mixture. Chill at least 1 hour

Make & Bake Pâte à Choux

1. Preheat oven to 425º
2. In a medium saucepan, add water and butter. Bring to a boil. Once at a boil, butter should be melted. If lumps of butter remain when boiling begins, remove the pan from the heat and wait until the butter has melted
3. Add salt and when the butter has melted in the water, remove the pan from heat and add the flour all at once. Stir the mixture with a wooden spoon until the mixture resembles mashed potatoes
4. Return pan to medium heat. Stir vigorously to dry out the pastry, which should take about 5 minutes
5. Add dough to electric mixer (or, this can also be done by hand) add the 5 eggs, 1 egg at a time, beating on medium-low speed. When the eggs are added, the dough first separates into strands, but will cohere with more beating. The pastry should now be soft enough to cling to the side of the bowl/spoon. (Note: After incorporating all the eggs, if the pastry is not soft enough to cling to a spoon, you may need to add a little more egg so that the pastry will puff correctly when baked. Beat an egg in a small cup and add a little of it to the pastry, blend well)
6. Line 2 baking sheets with parchment paper. Spoon pastry dough into a large pastry bag fitted with a ½" plain tip. Pipe about 55 mounds onto the baking sheets, each about 1½" in diameter, leaving 1½" between mounds
7. Dip finger in remaining beaten egg to smooth down the pointed tip of each mound
8. Bake puffs for 10 minutes, then reduce oven temperature to 400º and bake puffs 20 minutes longer (or until puffed and golden)
9. Turn off oven, let puffs sit in the cooling oven for 30 minutes before transferring to racks to cool completely

Prepare Puffs for Filling

1. With a skewer or chopstick, poke ¼" holes in bottom of each puff. Puffs may be made 2 days ahead and kept in an airtight container

Make Chocolate Sauce

1. Bring whipping cream to simmer in small saucepan. Remove from heat. Add chopped chocolate, stir until chocolate is melted and smooth
2. Cool sauce until lukewarm

Fill Puffs

1. Transfer chilled pastry cream mixture to a large pastry bag fitted with a ¼" plain tip. Stick pastry tip into the hole in the bottom of each puff, and fill until the mixture almost starts to come out of the bottom (but do not over-fill)

Assemble Croquembouche

1. Using tape, cover a craft Styrofoam cone with parchment paper. Place on turn-table or platter
2. Working with 1 cream puff at a time, dip bottom in chocolate sauce, leaving top ⅓ uncoated, letting excess drip off. Arrange 1 ring of puffs around base of cone, placing as closely together as possible
3. Insert toothpick through each puff into cone to attach puff to cone, leaving end of toothpick sticking out (you'll push it in later with thimble).
4. Attach 2nd ring of puffs above 1st, again packing tightly, staggering so puffs in 2nd ring are not directly above puffs in 1st ring. Finish covering cone and top with 1 puff
5. Using a thimble, push in toothpicks. Decorate with chocolate sauce, chill in refrigerator until serving or displaying