Shrimp Thermidor

1/4 cup green onions or shallots, sliced
2 Tablespoons diced green pepper
3/4 cup fat−free half−and−half
4 slices Smart Beat fat−free cheese, cut in pieces
1 can (10 oz.) potato soup
2 tablespoons lemon juice
1/4 teaspoon ground pepper
1/2 teaspoon dry tarragon
1/2 teaspoon dry mustard
1 − 1 1/2 cups cooked shrimp (tails removed)