Grease the wells of a muffin tray (12 mm) and dust with flour.
Put the ingredients for the shortcrust pastry in a bowl and knead briefly with your hands to form a smooth dough. Divide this into 12 portions and place one of them flat in a recess and press it down to the top with lightly floured hands.
Put a teaspoon of jam in the middle and smooth it out with the back of the spoon.
For the batter, mix all ingredients with the hand mixer to form a smooth dough. Spread evenly on the jam with two teaspoons. The batter rises nicely during baking, so don`t be surprised if the batter looks like little in terms of quantity.
Bake the tartlets at 180 ° C for 20-25 minutes on the middle to lower rack. After baking, let it cool down for 5 minutes, then remove it from the mold and let it cool down on a wire rack.
For the topping, mix lemon juice or water with enough powdered sugar until you have a whitish, thick paste. Put half a teaspoon of icing on each tartlet.