Melt butter or fat in pan.
Whisk in flour until browned a bit.
Whisk in stock.
Whisk in ketchup, Worcestershire, mustard, and spice.
Bring to boil until thickened.
Add cream, milk, more stock if it becomes too thick.
Strain with fine mesh sieve to remove lumps. Press with spatula to get the good stuff.
Add a pat of butter for a nice shine.