Melt one tbsp of butter and toss the onion and cook until it’s slightly transparent.

Add the meat and season with mustard, salt, and pepper. Cook until it’s fully cooked and there is no trace of pink in the meat.

Drain the meat and save it for later.

In the same pan melt the other tbsp of butter and add the flour. Whisk vigorously and when the butter and flour made and homogeneous paste, pour slowly the milk and keep whisking until the roux is formed.

Then add the cooked meat and season with the nutmeg and cayenne pepper. Adjust the salt and pepper to taste.

Toast the bread. Pour some of the meat sauce over the bread. Sprinkle with some parsley and serve.