Cut the butter in small cubes and combine with all the ingredients in a machine bowl fitted with a paddle attachment.
Mix on medium speed until a crumbly mixture is obtained. Remove from machine.
Between parchment paper or plastic roll the streusel 2 credit cards thick. Place in freezer until hard.
Cut the streusel in pieces 10% smaller than the piped pate a choux and place on the piped choux paste pieces.
Place in oven and bake.
Pâte à Choux
240g unsalted butter, cubed
20g extra fine sugar
285g bread flour
480g egg, loosely beaten
In a saucepan bring to boil the water, milk, sugar, salt and butter.
Remove from heat and immediately stir in sifted flour. Stir well until combined. Return to heat and stir until the dough releases from the sides and bottom, about 2 minutes.
Place the mixture into a bowl fitted with the paddle attachment, on medium speed gradually add the eggs, one at a time, scraping the bowl often. Once 420 g of the eggs are added examine the batter, it should be smooth and have a light sheen. It should be firm enough to hold its shape when piped. Add the remaining egg if needed.
Pipe the batter using a plain tip on parchment lined sheet pans.
Cut the streusel in circles 10% smaller than the piped pate a choux and place on the surface.
Place in a (lightly steam injected) oven at 350°F with steam vent closed. When the products are well expanded, open the steam vent (or part oven door) to let the steam escape. Bake until the products is firm crisp when pressed on the sides. About 30 minutes for profiteroles.