Chop the onion.

Measure the dry mustard.

Slice the bratwurst into 3/4 inch pieces.

Drain the sliced mushrooms.

Cook onion and mustard in margarine or butter in a skillet over medium heat until tender, about 5 minutes.

Stir in the sliced bratwurst, beer, mushrooms, beef broth, sugar, and pepper.

Simmer for 5 minutes, stirring occasionally.

In a separate bowl, stir flour into sour cream until smooth.

Gradually whisk some of the hot pan juices into the sour cream mixture to temper it and prevent curdling.

Stir the sour cream mixture into the bratwurst mixture.

Cook and stir until the sauce has thickened and is bubbly, about 2-3 minutes.

Cook and stir for 1 minute more.

Serve hot over cooked noodles.

Sprinkle with snipped parsley for garnish.