Preheat oven to 400°F
Place the bread onto a parchment-lined baking sheet, brush with olive oil, and toast until golden brown
To a large skillet, over medium-high heat, add 3 tbsp butter. Once the butter melts, add the sliced onions and season with salt. Continue to cook the onions low and slow until they begin to caramelize and turn a deep golden brown. This could take 30 minutes, but it’s worth it!!
Add thyme, bay leaves, and sherry. Cook for about 4 minutes or until the alcohol smell is gone.
Add stock, and increase the heat to medium-high. Bring to a simmer and let simmer for 5 minutes. Remove thyme sprigs and bay leaves, and mix in the chicken and parsley
Top with toasted bread and Gruyère cheese. Bake for 20 minutes.
Garnish with chives.