1 qt. Milk
8 oz. Sugar
4 Egg Yolks
2.5 oz. Cornstarch
2 oz. Butter
Heat the milk and about half the sugar until it's ~steamy~. Combine the remaining sugar and cornstarch in a small cup to make sure there are no lumps. In separate bowl, whisk whole eggs and egg yolks and add the sugar/cornstarch mix about 1/3 at a time. Whisk for a few minutes (one teacher says just get it good and mixed, one says mix till it holds some air and when it drops off the whisk and keeps it's shape, like a ribbon, it's ready). Both work, why whisk your arm off?
When the milk is steaming, temper it into the egg mixture. If you don't know what that means,
Add about half of the milk into the egg, and whisk really well, until it's combined. Add the hot, milky, egg mixture back into the pot. Stir ccoonnssttaannttllyy on med-high heat for 1-3 minutes. The mixture gets very thick, very fast. Keep stirring. It will boil. Keep stirring. This cooks the eggs, and kicks out the starchy flavor.
After a minute or so, remove from heat and place in a clean container. Now stir in the butter, and a drop or three of vanilla if you want. Cover with plastic wrap directly on the surface of the creme, and cool until use.
Cream Puff filling -
Once cooled, it will be thick. Whisk by hand or machine until loose. Fold in 14-16 oz whipped cream. Keep refrigerated until needed.
If you like, you can dip your eclairs or puff in ganache. I would recommend dark chocolate. 2 parts chocolate to 1 part heavy cream.