In a sauce pan add the butter to the water and bring to a boil. Once the butter is fully melted, dump in the flour and cocoa all at once and stir vigorously until the batter comes together into a ball.
Dump the dough ball into a mixer fitted with a paddle attachment and beat in the 4 eggs, 1 at a time until fully incorporated.
Put the batter into a piping bag and pipe small, 1/2 inch blobs onto a baking sheet, spaced at least an inch apart.
Make the craquelin
Mix the butter, sugar, and flour until it creates a pasty dough.
Divide into three portions and color red, green, and yellow or other colors as desired. Roll out the dough into a thin sheet. During this you can put blobs of the different colored doughs together to make a short of marbled coloration. Freeze for 10 minutes.
Cut circles out of the craquelin, roughly the same size or smaller than the unbaked cream puffs. Place one circle on top of each puff.
The cream puffs are ready for the oven.. Bake at 400 until they turn golden brown.
Make the cream
Whip vanilla, cream, and sugar on high until stiff peaks form.
Fill the cream puffs
Put the cream in a piping bag fitted with a filling tip (or you can poke a hole in each cream puff and just use a pastry bag without a tip, but this is a bit more challenging). You can also cut the cream puffs in half if you want to fill them without using a pastry bag at all, but it won't look quite as nice.
Insert the tip of the pastry bag into the bottom of each cream puff and fill them up! Eat within a few hours so they keep their nice texture and don't get soggy.