Bring milk, 100 ml water, fat, salt and 1 teaspoon sugar to the boil in a saucepan. Add flour at once, stir with a wooden spoon until the dough separates from the bottom of the pot as a lump. Put the dough into a bowl and immediately stir in 1 egg.
Allow to cool for 5-10 minutes and stir in 3 eggs one after the other. Let the choux pastry rest for about 30 minutes. Pour into a piping bag with star-shaped spout. Line a baking tray with baking paper and spray a ring (approx. 24 cm Ø) in the shape of a flower on it.
Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for 30-35 minutes on the 2nd rack from below. Remove, immediately cut in half with scissors and let cool. In the meantime, soak the gelatine in cold water for about 5 minutes.
Boil up lemon juice and 100 g sugar. Squeeze out the gelatine well and dissolve in it. Stir in 3 tablespoons of buttermilk and stir into the remaining buttermilk. Chill for about 45 minutes. In the meantime, wash the strawberries, drain and pat dry.
Clean and halve the strawberries. Whip the cream until stiff. As soon as the buttermilk begins to gel, fold in the cream and chill for about 15 minutes. Spray the buttermilk cream onto the bottom base in a wave-like pattern.
Spread the strawberries as desired. Place choux pastry lid on top, arrange on a cake plate and dust with icing sugar.