Know your béchamel is done: when it is thick enough it will “coat the back of a wooden spoon,” which means dip your spoon into the béchamel and then draw a finger through the coated spoon. The sauce shouldn't run together, and you should see a clean line. The sauce will wipe clean and leave an open space. The béchamel is done and ready when it sticks to the spoon, as in this photo of the spoon on the pot of bechamel. STORING Bechamel Sauce: You can make and store bechamel for up to 5 days in an airtight container in the fridge