Make a shortcrust pastry with the ingredients except plum jam and egg yolk. Wrap two equal portions of it in foil and refrigerate.
Use 2/3 of a portion of dough for the base, roll out and press into the mold. Spread jam on top and roll out the last third of the dough. Thread out strips for a grid or cut out shapes. Put this on the jam.
Brush with egg yolk and bake at 175 degrees for about 40 minutes.