Cook pasta to an al dente texture according to instructions on the package and rinse in a colander under cold water to stop cooking.
In a large saucepan bring milk and bay leaf just to a boil and set aside so the flavour can infuse.
In a large dutch oven or brasier melt the butter. Add chopped onions and sauté for a few minutes until translucent - approximately 5 minutes.
Add flour one tablespoon at a time and whisk constantly over low heat until combined. Do not brown. Add a ladle of milk with each additional tablespoon of flour if mixture becomes too thick.
Continue adding a ladle of warm milk and whisking after each addition to ensure there are no clumps. Remove the bay leaf and discard.
Once all milk has been added and the sauce has thickened add paprika and 1/4 teaspoon freshly ground pepper and turn off heat.
Slowly add the grated cheese to the sauce and stir until melted. Taste and season with extra salt or pepper as necessary.
Mix cheese sauce together with pasta and stir in optional vegetables.
Pour into your 9 x 13 inch baking dish or keep in your brasier. It will seem like a lot of sauce. Sprinkle with breadcrumbs. Bake for 20 – 30 mins, until top is golden brown and bubbly.
Just before dinner bake at 350 degrees for 20 – 30 mins, until top is golden and bubbly.