In a large bowl, whisk the egg yolks until combined. Add in the cornstarch and half of the sugar. Whisk again until creamy

In a large saucepan, bring the milk and the other half of the sugar to a boil. Remove from heat

Carefully, temper the eggs, that means to bring up the temperature of the yolks without cooking. To do that, add a bit of the hot milk mixture into the yolks while whisking vigorously. Then slowly add the rest of the milk mixture. Do not stop whisking 

Pour the whole mixture back into the pot and cook over medium heat until the mixture thickens

Strain the pastry cream into a clean bowl and add the vanilla and butter. Stir until butter melts 

Cover the bowl with plastic wrap. Make sure the plastic wrap touches the pastry cream directly (to avoid creating a film) 

Refrigerate for 2 hours or until completely chilled. 

Make 5" straight lines in parchment paper using a pencil. Turn the paper over and use it to line a sheet pan

In a large pot, heat the water, butter, milk, sugar, vanilla and salt on medium heat until the mixture boils

When the mixture boils dump all the flour at once and mix vigorously with a wooden spoon until all the white specks disappear and the dough pulls away from the walls of the pot

Place the dough in a mixer fitter with a paddle attachment and mix on medium speed for a few minutes to cool down the dough

In a small bowl, whisk all the together until combined

Slowly add the eggs into the dough while the mixer is still running

Pate Au Choux should be shiny and hold its shape

Place dough in a piping  bag fitted with a star tip

Using the straight lines as a guide, pipe the eclairs onto the parchment paper lined cookie sheet

Freeze dough for a couple of hours

Preheat oven to 350 degrees F

Bake for 35-45 minutes or until eclairs are golden and firm to the tough

Remove from heat and cool 

Make 3 holes on the bottom using a knife or piping tip

Place all ingredients minus the teaspoon of milk in a bowl. Mix until combined. If needed add the teaspoon of milk

Add the food color of your choice (if desired)

Glaze should be thick but still pourable

Place chilled pastry cream in a piping bag fitted with a small tip

Pipe in the cream into each of the holes of the eclair until the pastry feels full

Clean the bottom of the eclair with a spatula

Dip each eclair into the glaze while shaking off the excess. Decorate with sprinkles (optional)