Bechamel sauce is a creamy white sauce perfect for pouring overstuffed cannelloni for extra creaminess. In a small saucepan over medium heat, warm 1 cup of milk. In a separate sauce pan over medium heat, melt 2 tablespoons of butter. Add 2 tablespoons flour and whisk for 1-2 minutes until smooth. Slowly add in the milk and whisk for 2-3 minutes until thickened and bubbling. Pour over the casserole dish and tubes.