Preheat the oven to 425°F. In a medium saucepan, add the butter, salt, and 1 cup of water. Heat over high heat until boiling, and then add the flour and stir constantly with a rubber spatula or wooden spoon. NOTE: These first few steps will go quickly--I recommend reading ahead and having everything laid out ahead of time. The choux will thicken quite quickly, coming together in a sticky ball/paste. Lower the heat to medium and continue to cook while stirring constantly for another minute.
Remove from the heat and let cool for a minute. Add the choux to the bowl of a stand mixer, and mix on medium speed for a few minutes to allow the dough to cool a bit more and break up a bit. Bring the speed up to medium-high, and add 4 eggs, one at a time. Pause as necessary to scrape down the sides, you want to ensure a VERY smooth dough. Once all 4 eggs are added, the dough should be thick and smooth.
Line a baking sheet with parchment. Add the dough to a pastry bag and pipe 12-14 mounds of dough (they'll likely look like large hershey's kisses). Leave space between them as they will puff up, and you want them to be roughly 2 1/2" in diameter. Wet the tip of your finger with clean water and gently pat down the little tips of dough left behind from the piping, and then gently brush the tops with the egg wash. Bake for 10 minutes at 425°F, and then reduce the temperature to 375°F. Bake for an additional 20-25 minutes, until brown and crisp. Remove from the oven and with a cake tester or tooth pick, poke a small hole in the tops (or near the top) of each choux puff. This will allow steam to escape, helping to keep them nice and crispy.
Once cooled to room temp, slice in half and scoop your favorite ice cream in between the two halves, and top with chocolate sauce (recipe below) and powdered sugar. Any unused puffs can be frozen to use later, just pop them in the oven at 400°F for 10 minutes!
