Melt the butter in a saucepan and cook the onion and garlic in it until golden. Blend in the flour. Remove from the heat and stir in the turkey stock and cream. Cook, stirring, until the mixture is medium thick. Add the turkey, seasonings and lemon juice. Turn into a one-quart casserole.
Top the casserole with sage cornmeal pastry. Trim, turn under, and flute the edges of the pastry. Cut two or three gashes in the top to allow for escape of steam. Bake for about twenty minutes, until brown.