In my version of pan sauce, I used the drippings from meatballs fried in plenty of butter.The meatballs were removed from the heat and kept warm in an ovenproof dish in the oven while the sauce was made.Turn up the heat to high and add the stock. I always have a lot of stock at home, but you can always use a bouillon cube (or as I recommend "Fond du Chef") with water. Let it boil for 5 minutes together with the cooking water from, for example, potatoes. It adds extra flavor.Make a flour-milk mixture from the flour and milk and slowly add it to the sauce while stirring vigorously.Turn down the heat.Add mustard, Worcestershire sauce, ketchup, and browning, still stirring.Season with salt, pepper, and lemon juice.