For the gratinated Beiried slices, pound the Beiried slices until tender, salt, pepper and brush with mustard on both sides.
Heat a mixture of oil and butter in a frying pan and fry the beirie slices on both sides. Remove, wrap in aluminum foil and let rest until warm.
Peel and finely chop the shallots. Heat the butter in a frying pan and fry the shallots until golden. Add thyme and parsley and roast briefly.
Cut the toast into small cubes and place in a mixing bowl. Add the egg and cream, season with salt, pepper and nutmeg and pour over the shallot mixture. Mix well.
Place the beiried slices side by side in a baking dish and spread with the toast mixture. Bake in the preheated oven at 200 °C for about 8 minutes.
Serve the gratinated beirie slices with leaf salads.