Preheat oven to 190ºC F. In a small saucepan, melt butter. Stir in flour. Cook and stir 2 minutes. Stir in stock and milk. Cook, stirring constantly, over medium heat until thickened; remove from heat. Stir in onion, chilies, salt and cheese. Arrange half a sliced egg and 1 rounded tablespoon ham on each tortilla. Spoon about 2 tablespoon cheese sauce over ham. Fold both sides of each tortilla over filling; then fold top and bottom to slightly overlap in center. Place filled tortillas, folded-side down, in a shallow baking pan. Cover with foil. Bake in preheated oven 10 to dozen minutes or until heated through. Serve warm. Makes 6 servings.