In a large pot, sauté the sliced onions in a little olive oil until they become translucent.

Add the flour and stir vigorously.

Pour in the chicken broth and add the thyme. Season generously with black pepper and bring to a boil, stirring.

Reduce the heat and simmer for 15-20 minutes.

If you like, add cheese on top and broil in the oven for a few minutes until golden and bubbly.