2. Melt butter in a pot. Addonion and bacon and cook for 4 or 5 minutes without browning. Add flour and stir for 2 minutes. Slowly add milk, stirring until sauce has thickened. Stir through thyme, half the cheese, and season with salt and pepper.
3. Add pasta and stir, coating it in sauce. Spoon into individual dishes or one large dish. Sprinkle on remaining cheese. Place in hot oven for 20 minutes or until golden.