For the choux pastry, put water, butter and salt in a pot and bring to a boil.
Remove the saucepan from the heat, mix the flour, cocoa, cornstarch and baking powder together and then add it all at once to the hot liquid and mix it with a spoon to a smooth dough.
Burn off the dough by heating the dough for about 1 minute while stirring or turning it back and forth. Then transfer the dough to a bowl.
Using a mixer, beat the eggs into the batter one at a time, slowly, until it is shiny and has peaks that stick to a knife or spoon.
Place the batter in a piping bag and then pipe onto a baking sheet lined with parchment paper in the shape of cream puffs. (The cream puffs will rise a lot when baked, remember this when piping).
Bake in a preheated oven at 200° C top/bottom heat for about 20-25 minutes. After baking, cut off the top directly and then let cool.
Chop the couverture and melt over a water bath. Spread the melted couverture on the bottom of the cream puff and place a washed, degreened strawberry on top.
Whip the cream with the sifted powdered sugar and San-apart/ cream stiffener until stiff. Place the stiff cream in a piping bag and carefully pipe onto the strawberries, then place the lid on top.