Recipe: a way of using left over roast beef: leftovers

I don't know what to call this.  It's certainly not a stroganoff, but it is jolly tasty for some very simple ingredients.
All the ingredients are leftovers apart from the mustard, the salt and the pepper.  Oh, and the butter.

Ingredients to serve 1
A dollop (small) of butter
A small wedge of onion, thinly slices
A bit of yellow pepper (about an eighth)  sliced
three or four mushrooms
Some leftover sliced roast beef, shredded
Some cream
Some Dijon mustard
Some salt and pepper

Method
Melt the butter and gently saute the onion, pepper and mushroom until soft.  Add the beef and continue sauteing
Add the butter, a dollop of mustard to taste and the salt and pepper.  Stir well and leave to heat slowly.

Done

I ate it just as it was, no other carbs.  You could use rice or pasta or mash.

Whatever it is called, it's tasty!