Cheesy Potato Soup

4-5 c potatoes
1/4 c margarine
3 c chicken broth
1 tsp Worcestershire sauce (Kroger brand is GF - check other brands before using)
1/4 c finely chopped onion
1/2 c GF flour (rice flour works well)
2 cups milk
1 cup shredded cheese

Chop potatoes and boil until tender. Drain and set aside. Saute onion in margarine. Stir flour into onion and margarine mixture then add milk and broth. Heat until thickened. Add Worcestershire sauce and cheese, then potatoes. Heat until completely warmed.