• Preheat oven for 425° Fahrenheit and line a large baking sheet or two smaller baking sheets with parchment paper. Set aside.
• Place the butter, water and salt in a medium-size saucepan over medium heat and bring to boil. Once mixture is boiling, remove from heat and with a wooden spoon or spatula, quickly add the flour. Return to heat and stir constantly until the dough comes away from the sides of the pan and forms a thick, smooth ball (about 2 to 3 minutes).
• Transfer the dough to the bowl of a stand mixer fitted with a paddle (or you can use a handheld mixer). Beat with a mixer on low speed a minute or two to release the steam from the dough. Once the dough is lukewarm start adding the eggs one at a time, (the mixture will look curdled at first, but will begin to come together as the mixer runs). Mixing on medium-low speed until each egg is fully incorporated, about 30 to 45 seconds per each egg. Continue to mix until you have a thick, shiny and smooth pipe-able consistency.
• Transfer mixture to a pastry bag and pipe onto prepared baking sheet, creating a 2-inch circular ball. Pipe at least 2 inches apart from each other. They will expand after baking. 

  Add 1/4 cup of water to a small bowl. Dip your finger in the water and press down the little peaks at the top of the dough, so the puffs are smooth.
• Bake at 425°F for 25 to 30 minutes or until the shells have golden brown. Do not open the oven door!
• Remove from the oven, and while the puffs are still hot, quickly prick each puff with a toothpick to create a small hole. This allows steam to escape and prevents them from collapsing. Return the puffs to the tray and place them in the turned-off oven with the door partially open for 4–5 minutes.
• Once the time has passed, remove from oven and allow to cool completely on baking sheet.
• Piping the Mascarpone Cream - Add the whipped cream to a pastry bag. Use a serrated knife to cut the shells in half, creating a top and bottom. Evenly pipe the mascarpone cream into the pastry bottoms, then gently place the lids on top of the cream. 
• Lightly dust the tops of each cream puff with powdered sugar just before serving, as the sugar will dissolve in the refrigerator if not served right away.

Mascarpone cream filling

• In a large mixing bowl, combine heavy cream and powder sugar. Beat on medium-high speed until fluffy with stiff peaks. Add the mascarpone cheese. Beat at high speed for a few minutes until mixture comes together, thickness and resembles frosting.