Cook egg noodles or any type of pasta according to the instructions on the package.
While noodles are cooking, rinse and drain sauerkraut and cut kielbasa into small pieces.
Melt butter in a microwave or on a saucepan at low heat.
Chop onion and garlic and stir them a few minutes in a deep frying pan at a medium heat.
Add cold milk, pepper, mustard and flour and stir well.
After a few minutes, when the flour is mixed well with milk, add cheddar cheese and stir. Lower the heat if necessary.
When the cheese is melted, add kielbasa and sauerkraut and stir well for a few minutes on a low heat.
Toss everything in a baking pan and top the casserole with bread crumbs and butter. You can first mix bread crumbs with butter. Bake at 200 degrees Celsius for 20 minutes or until golden.