Preheat oven to 400 degrees. Line 2 baking sheets with parchment paper.

In a heavy bottomed saucepan, combine butter and water. Bring to a boil on medium heat.

In a separate bowl, combine flour, sugar and salt. Whisk together.

When butter water is boiling, remove from heat and add flour mixture using a wooden spoon.

Continue to combine until a smooth ball forms that is no longer sticking to the sides.

Return pan to medium heat and continue to mix constantly for 2 minutes.

Remove from heat and place dough into a mixer fitted with a paddle attachment or your hand mixer.

Mix for 2 minutes on low to cool down.

In a small bowl combine 4 eggs and whisk together.

Slowly add ⅔ of egg mixture to your dough and mix on low.

Increase you mixer to medium high and continue to mix until dough becomes thick again.

Add the rest of the egg and mix again for about 2 minutes.

Scoop out tablespoon rounds 2 inches apart on your baking sheets.

Bake for 15 minutes at 400 degrees then reduce temperature to 350 degrees and bake for another 15-30 minutes, depending on your oven.

Keep an eye on them, if they begin to brown too quickly turn your oven off.

Once done, remove from oven and make a small whole using a toothpick into the puffs.

Return baking sheets to a hot (but turned off oven) and allow to cool with the oven door cracked open slightly (I folded a oven glove to keep door open slightly).

Allow puffs to cool completely in oven (about an hour).

In a heavy bottomed sauce pan, bring milk to a boil on medium low heat.

In a separate bowl, whisk egg, egg yolks and sugar together until pale yellow. Whisk in cornstarch until smooth.

When milk has come to a boil, remove from heat and slowly add ¼ a cup or hot milk to the egg mixture, stirring constantly.

Repeat with another ¼ cup of hot milk (so that the eggs don't cook due to the hot milk)

Next add the entire egg/milk mixture to the pan with the remaining milk.

Add the chocolate.

Mixing constantly, return the pan to medium low heat until it coats the back of the spoon.

Once mixture has thickened, remove from heat and add butter and vanilla.

Pour into a bowl and cover with plastic wrap. Refrigerate until cold.

Once cold, either cut puff in half and fill or pipe into puff rounds.

If desired drizzle with chocolate ganache or simply sift with powdered sugar.

Can be filled and served immediately or filled and refrigerated for later in the day.

These also freeze really well!