Cook macaroni according to package directions.
In large saucepan, melt butter. Add onion and cook until tender. Stir inflour, salt. mustard, salt and pepper. All milk slowly, stirringconstantly, and cook until sauce is thickened and bubbly. Add cheese andstir until melted. Combine cooked macaroni and cheese mixture and mixwell. Pour into buttered casserole. (I use one that's about 30 cm square).
Top with topping and bake in 375 oven for 20 25 minutes.
To make topping: tear roll apart and use steel blade of food processor tochop into fine bread crumbs. Melt better in small saucepan then add crumbsand toss until covered with butter. Combine buttered crumbs with cheese andspread over casserole.
I generally serve this with sauteed Kielbasa.