6 boneless, skinless chicken thighs
1 teaspoon kosher salt
½ teaspoon freshly ground black pepper
1 tablespoon olive oil
1 tablespoon unsalted butter
1 onion, sliced
3 garlic cloves, minced
2 cups sliced mushrooms
One 14.5-ounce can diced tomatoes
One 28-ounce can crushed tomatoes
2 tablespoons Italian seasoning
Season the chicken on both sides with salt and pepper. Heat the butter and oil in a large skillet over medium-high heat. Add the chicken to the skillet, and cook for about three minutes per side, until browned. Transfer the chicken to the slow cooker.
Add the onions and garlic to the skillet and cook, stirring frequently, until softened, about 5 minutes. Add the mushrooms and cook, stirring frequently, for about 5 minutes, until softened. Transfer the vegetables to the slow cooker.
Add the diced and crushed tomatoes, Italian seasoning and the remaining salt and pepper to the slow cooker.
Cover and cook for 6 hours, until the chicken is cooked through and very tender.
Serve hot.