Method

Put oil in a saucepan on a med to high heat, once oil's hot carefully/slowly add chopped onto the oil, you may need to do in batches, cook until nut brown, remove with slotted spoon or small sieve & place on kitchen paper to drain.

Place a saucepan over a med heat, add the butter when it melts, add flour stir in until it bubbles, add the milk slowly whisking all the time until all used, add the onion & cook until onion is soft.

Either use a stick/hand blender or in a food processor blitz to a smooth sauce, add cream & seasoning stir & re-heat & serve.