Preheat your oven to 375°F (190°C). Pat the chicken breasts dry with paper towels. In a small bowl, mix the smoked paprika, garlic powder, salt, and pepper. Season the chicken on all sides with this mixture.
Place a Dutch oven over medium-high heat and add the olive oil. Once the oil is shimmering, carefully place the chicken breasts in the pot. Sear for 3-4 minutes per side, until golden brown. You may need to do this in two batches. Transfer the seared chicken to a plate.
Reduce the heat to medium. Add the butter to the Dutch oven. Once melted, add the chopped onion and sliced bell peppers. Cook, stirring occasionally, for 5-6 minutes until they begin to soften.
Add the sliced mushrooms and minced garlic to the pot. Cook for another 2-3 minutes, until the mushrooms have released some of their liquid and the garlic is fragrant.
Pour in the can of diced tomatoes (with their juices), chicken broth, and Worcestershire sauce. Stir everything together, scraping up any browned bits from the bottom of the pot. Bring the sauce to a gentle simmer.
Nestle the seared chicken breasts back into the sauce in the Dutch oven. Spoon a little of the sauce and vegetables over the top of the chicken.
Cover the Dutch oven with its lid and carefully transfer it to the preheated oven. Bake for 15-20 minutes, or until the chicken is cooked through.
Check that the internal temperature of the chicken has reached 165°F (74°C) with a meat thermometer. Let the dish rest for 5 minutes before serving.