Line a baking sheet with parchment and pre heat oven at 390 F
Bring the milk to a gentle boil and then turn off heat. Add the seeds from the vanilla sticks and cover with a lid. Let the milk infuse with vanilla flavors.
In a medium large pot add water, milk (the one without vanilla), butter and a pinch of salt and bring to a rolling boil. Turn the heat off and remove the pan.
Immediately add flour, gradually, and mix well with a whisk until well combined and no lumps left.
Allow the dough to cool a little then add eggs, one at a time, mixing well after each egg is added until fully incorporated. You need the composition to look and feel like soft chewing gum and be sticky. If not, add one more egg.
Transfer the dough to a large pastry bag fitted with a flower tip. Pipe rounds onto each prepared pan and do a little swirl for a more spectacular result. If you don't have a flower tip: with a spoon to drop a dollop of dough (about the size of a large walnut) in the baking sheet but not very close to each other (about 2" apart).
Bake for about 20 minutes. Do not open the oven for the first 15 minutes!
When all dough is done and baked, let the puffs cool completely before cutting in half, horizontally.
To make the custard filling
Take the 16 yolks and mix with sugar, beat well with a mixer until smooth. Then add flour and beat well. Add the vanilla infused milk gradually. Move everything to a saucepan and bring to a rolling boil while stirring continuously with a whisk until stiff.
Remove from heat and add butter. Cool completely before using as filling for the choux's.
To make the whipped cream
Then make the whipped cream as indicated in my whipped cream recipe
Assemble the cream puffs
Fill the puffs with vanilla cream and whipped cream.