Baked French Onion Soup

2 oz butter
1 pound onions, sliced
1/2 clove garlic
1 teaspoon flour
4 cups beef stock
salt and pepper
2 oz gruyere cheese (used mozz)
1 tsp dijon mustard
4 slices french bread

Melt butter in large saucepan and add onions. Very slowly, brown the onions. (should take 1 hour!)
Add garlic to onions after 45 minutes.
Add flour and cook for 1 minute at medium.
add stock, and stir until it boils. Season with salt and pepper, simmer for 20 minutes.
Preheat oven to 400f. Mix grated cheese, mustard, pepper. Spread on bread. Put bread in bottom of bowls, and ladle soup over top.
Make in oven until cheese floats and browns on top.