In a large skillet, melt 2 Tbsp of butter over medium heat. Once melted, add the chicken thighs, seasoning with salt and pepper. Brown them for about 4-5 minutes on each side until golden brown. Remove the chicken and set aside.

In the same skillet, add the remaining butter. Sauté the sliced shallots and garlic until softened, about 2-3 minutes.

Add the sliced mushrooms to the skillet. Cook until they release their moisture and become tender, around 5 minutes.

Sprinkle the flour over the sautéed vegetables, stirring well. Cook for another minute to eliminate any raw flour taste.

Pour in the white wine and cognac to deglaze the pan, scraping up any brown bits stuck on the bottom.

Stir in the chicken stock, crushed tomatoes, tarragon, and parsley. Bring it to a gentle simmer.

Place the browned chicken thighs back into the skillet. Cover and let it simmer for approximately 30 minutes or until the chicken is cooked through and tender.

Before serving, taste the sauce and adjust seasoning with salt and pepper as needed.