For the blueberry apple tartelettes, knead the flour with the egg, cold butter, cinnamon, nuts and powdered sugar to make a shortcrust pastry.
Let the dough rest a bit, then roll it out on flour and cut out 12 apples with a template. Cut out the center of 6 apples and use a little water to glue the pieces without centers onto the pieces with centers, creating a border for each.
Grease a tray with 6 apple shapes and place the dough in it, raising the edge a little. Peel and core the apples, cut them into small pieces and mix them with the sugar and blueberries.
Divide this mixture among the 6 apple pans and bake at 180 degrees top/bottom heat for about 20 minutes, until the dough turns brown.