Preheat oven to 400°. Line baking sheets with parchment paper or use a silpat.

Combine butter, sugar and water in a medium saucepan over medium heat. Bring mixture to a boil, then quickly stir in the flour, stirring continuously with a wooden spoon. Continue to heat and stir until mixture appears dry on the bottom of the pan. There should be a light film formed on the bottom of the pan.

Remove from the heat and transfer to a large bowl. Stir in 4 eggs, one at a time, Stir vigorously between egg additions (alternatively, you can use a stand mixer with the paddle attachment). Dough will be stiff and thick.

After thoroughly mixing, transfer mixture to a piping bag with a large plain tip attached. Pipe dough in approx. 2-inch circles. There is a silpat with circles marked that makes this process more accurate. Mix 1 teaspoon water into remaining egg and brush egg wash on top of each puff.

Bake for 15 min. then lower oven temperature to 350° and continue to bake for about 20 min. until nicely browned. Turn oven off and leave the oven door slightly ajar with puffs still in oven. You can insert a wooden spoon between the door and oven to help with this. Allow puffs to sit in oven until oven is just slightly warm. Remove to a cooling rack and cool completely.

Slice each puff in half and remove any excess dough from center.

In a medium saucepan, over a med-low heat, stir together eggs, sugar, lemon juice and zest, using a wooden spoon until the mix is creamy and smooth.

Turn heat to low and continue stirring until mixture thickens and coats the back of the spoon.

Add butter and stir well.

Remove from heat and allow to cool.

Beat cream cheese, powdered sugar, and vanilla until smooth and thick. Use a hand mixer or a stand mixer with the whisk attachment.

Slowly add the heavy cream while mixing on a medium setting. Continue whipping until the filling forms stiff peaks. It will resemble whipped cream but be thicker.

Fill a piping bag (with a large plain tip attached) with the lemon filling. Pipe the bottom of the puff full. Fill another piping bag (using a large plain tip or a large open star tip) with the whipped filling and pipe on top of the lemon filling. Be sure to pipe nice and full. Place 4-5 blueberries on top of cream filling. Place top of puff on top of the filling.