Preheat oven to 375 degrees.
In a large saucepan, heat Butter Olive Oil over medium heat. Blend in flour and add in bay leaf, stirring for 30 seconds. Pour in 1 cup of the milk, whisking constantly, until the mixture comes to a boil and is very thick. Pour in rest of milk in a slow stream, whisking continuously, until sauce comes to a boil and is smooth. Whisk in mustard.
Reduce heat to low and stir in cheese until melted. Remove bay leaf. Season with salt and cayenne pepper to taste and remove from heat.
Meanwhile in a large pot of salted boiling water, cook macaroni for 8 minutes or until just tender. Drain well and stir into cheese sauce until well covered.
Spoon into prepared casserole dish. Toss 1 tbsp. Butter Olive Oil with the bread crumbs and sprinkle mixture over the top of the casserole. Bake in preheated oven for 25 minutes or until bubbly and top is lightly browned
Prep: 15 minutes
Cook: 35 minutes
Makes: 4-6 servings