In a large skillet cook and brown the onion in the olive oil, about 10 minutes over medium heat.
Add ground beef and mince with edge of wooden spoon, cook until browned and done. Add salt & pepper to taste.
Add bacon grease and let that get heated up with the ground beef and onions.
Add the beef base and encorporate into the beef mixture. Add the flour and cook for about 5 -10 minutes to get the flour taste cooked out.
Slowly add the 1/2 & 1/2, stirring with wooden spoon. This will thicken quite quickly, so have the milk ready to go in. You may have to adjust the milk to make it thicker or thinner, just watch it as it gets thicker and thicker. Salt & pepper to taste.