For the finish
Add the macaroni to the sauce, sprinkle with pepper and stir well.
Spread the macaroni into a baking dish, top with the two kinds of cheese and bake in a pre-heated oven at 180 degrees C, until the cheese melts and the macaroni is golden on top.
For the sauce
Add the butter to a pot (large enough for the macaroni to fit in later as well) over medium heat and fry the bacon until lightly browned.
Add the flour and when smooth, pour in the milk and sour cream.
Bring to boil and immediately lower the heat. Simmer for a few minutes until the sauce thickens.
Remove from the stove, add the two kinds of cheese, season with salt and stir until the cheese melts.
Taste and season with salt if needed.