Mix flour and sugar, and cut in butter with a pastry blender. Add one egg, and stir with a fork until blended. Pat into a 9" quiche pan and sprinkle with chopped nuts. Place halved plums on top. Beat together two eggs, sour cream and sugar. Pour filling over plums. Bake at 350° for 1-1/4 hours, then brown at 375° for 10 minutes.