Preheat the oven to 350°F (180°C).

In a saucepan, combine the butter (cut into pieces), water, and sugar. Bring to a boil. Remove from heat, add the flour all at once, and mix immediately. Return to the heat and stir for 1 to 2 minutes to dry out the dough.

Add the eggs one at a time, mixing well and drying the dough between each addition, off the heat.

Using a piping bag, pipe a ring onto a silicone baking mat or parchment paper.

Sprinkle with sliced almonds and bake at 350°F (180°C) for about 35 minutes, until the pastry is dry and golden. Cool on a wire rack.

Whip the heavy cream until stiff peaks form, then fold in the mascarpone. At the end, gently mix in the chestnut cream.

Fill the choux pastry with this cream and enjoy.