Place oil, one tablespoon of butter and onions in a thick bottomed pot on medium heat. Sweat onions until transparent. Add celery, carrots, continue cooking for 8 mins, stirring often.
Add ground bison, garlic, few pinches of salt and pepper. Using a wooden spoon, lump meat into both parts crumble and larger chunks. Allow bison to slightly brown, but not stuck to the bottom, until no longer red in color. Stir occasionally.
Slowly pour in milk and stirring gently. Add nutmeg and allow to boil for 2-5 mins.
Add wine and cook for an additional 15 mins until some of the wine has evaporated. Add chopped tomatoes and tomato paste. Turn heat to 2nd lowest setting and allow to simmer, uncovered for 20 mins stirring often.
Check consistency throughout cooking and raise or lower the heat based on desired thickness.
Serve over buttered tagliatelle, crusty bread, or polenta.