In a small skillet, saute shallots in butter until tender; set aside.
In a large bowl, combine the flour, sugar, baking powder, salt and mustard.
Cut in butter until mixture resembles coarse crumbs. In a small bowl, combine egg and milk. Stir into crumb mixture just until moistened. Fold in cheeses and reserved shallot mixture.
Transfer to a greased 8-in. x 4-in. loaf pan.
Bake at 325° for 50-60 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to wire rack.