Steak w/Kumquats

Ingredients

• 1 pound "marinating steak"
• 1 cup orange juice
• 1 tbsp. prepared mustard
• 2 cloves garlic, chopped, or granulated garlic
• 1 large onion, sliced thinly
• 1/2 pound mushrooms, sliced
• 1 to 2 tbsp. oil
• 1 cup broth, vegetable or beef, or water
• 6 kumquats, washed and sliced into 1/4" rounds, seeds removed