Step 1

In a Dutch oven, or large heavy pot, sauté the onions and shallots with the oil and salt over medium to medium-low heat, until the onions are soft and golden, about 30 to 40 minutes, stirring often. You can cover them in between stirring to generate steam so they do not get too try dry. You want them caramelized but not browned.

Step 2

Add the flour and mix, cooking another 2-3 minutes. Add the white wine, sherry vinegar, thyme and bay leaves. Simmer uncovered to reduce the alcohol, about 10 minutes.

Step 3

Add the chicken bone broth and chicken. Bring to a boil then reduce heat to a simmer. Simmer until chicken is cooked through, about 25 to 30 minutes.

Step 4

Remove chicken and shred with 2 forks. Return back to soup. Taste for salt at this point and adjust to you taste as needed. Remove bay leaves and thyme;  ladle 1-½ cups soup into 6 oven-proof bowls.

Step 5

Place bowls on a baking sheet. Place sliced toasted bread rounds into each bowl and top bread with cheese. Broil on low on the 2nd rack from the top, until cheese melts, about 2-3 minutes.½