DirectionsSaute onions & mushrooms, drain.
Sear meat separately (leave meat medium rare), drain.
Mix 6 Tablespoons of Colman's powdered mustard with 6 Tablespoons of sugar & 2+/- Tablespoons of boiling water (just enough to make a very thick paste).
Let it sit for 15 min or so, allowing it to heat up.
Combine the meat, vegetables, and sour cream until well mixed.
Tablespoon by tablespoon, add the mustard mixture until you reach the heat level you want.
Put in the oven at 350 degrees for 30-45 minutes, until heated through.
Serve with french fries or shoestring potatoes.