For the dough, knead all ingredients with your fingers until smooth. Wrap in plastic wrap and refrigerate for about 1 hour.
Remove the stem of the strawberries. Stir pudding powder with 4 tablespoons of milk until smooth. Boil remaining milk with cream, sugar and vanilla sugar. Stir in the pudding powder, bring to a boil, then cover with foil to prevent a skin from forming. Allow to cool.
Using an egg whisk, stir in the egg.
Butter muffin tins. Roll out the dough thinly on floured surface and form 8 discs about 10 cm in diameter, place in the muffin cups and press down.
Put the strawberries in and fill with the custard. Preheat oven to 180 °C and bake with top/bottom heat in the middle for 30 minutes.
Let the muffins cool for 10 minutes, then remove from the muffins and sprinkle with powdered sugar.