Preheat the oven to 400°F (200°C) and line a baking sheet with parchment or silicone mat.

In a medium saucepan, melt butter with sugar and water over medium heat. Bring to a rolling boil.

Quickly stir in the flour all at once. Mix vigorously until a smooth ball forms and pulls away from the pan.

Remove from heat and allow the dough to cool slightly. Beat in the eggs one at a time, mixing fully between additions until smooth and glossy.

Transfer the dough to a piping bag fitted with a 2D or similar tip. Pipe rounds onto the prepared sheet, leaving space between. Make a small dip in the center of each using a spoon or piping motion.

Bake for 30 minutes until golden brown. Turn off the oven and let them sit inside for 10 minutes. Remove and cool on a rack.

To make the pastry cream, whisk egg yolks with sugar, starch, salt, and vanilla in a saucepan off the heat.

Gradually whisk in warm milk, place on the stove, and cook over medium heat, stirring until thickened. Let it simmer for about 3 minutes. Cool completely before using.

For pistachio cream: combine half the pastry cream with pistachio spread and optional green coloring. Whip heavy cream with powdered sugar until stiff, then gently fold it into the pistachio mixture.

Use a skewer to make a small hole in the side of each pastry. Fill the centers with pastry cream using a piping bag.

Pipe additional cream into the top center of each puff and dust with powdered sugar. Add a cherry or topping of choice.

Optional: top with pistachio cream instead and garnish with chopped pistachios.