Onion Cheese Soup

Directions

1. 1
   Melt butter in 4-quart saucepan over low heat.
2. 2
   Add onions and saute until lightly browned.
3. 3
   Add flour and cook an additional 5 minutes until butter and flour are well blended.
4. 4
   Slowly add milk and chicken stock, stirring constantly to prevent lumps.
5. 5
   Season with salt and pepper, continuing to stir until soup thickens. Whisk in egg yolk slowly and add cheese.
6. 6
   Simmer for another 5 to 10 minutes, stirring to prevent burning.
7. 7
   Remove from heat and serve immediately.