Make a thick brown sauce of butter, flour and stock: add seasoning, keep stirring and mix with meat and Mushrooms. Keep hot but care that it does not boil, or meat will get tough. Filling can be made in advance. Make smooth batter of the pancake ingredients. Heat butter in a 10 inch skillet. Use half of the batter; brown pancake slowly one side until done. Slide unto platter aand keep hot. Make second pancake in same way. Spread meat mixture on light side of first pancake and turn second, brown side up, on top of the first. Cut into wedges and serve at once with a green salad.