Start by heating 1 tablespoon of extra-virgin olive oil in a large skillet over medium heat. Once hot, toss in the diced onion. Sauté it for about 2-3 minutes until it becomes soft and translucent. Add the minced garlic and chopped bell pepper, cooking for another minute or so. Finally, toss in the sliced mushrooms and continue cooking until they soften.

While your veggies are getting settled in, grab a cutting board and your chicken. Season the chicken with salt and pepper on both sides. Heat the remaining 2 teaspoons of olive oil in the same skillet, and sear the chicken for about 3-4 minutes per side until golden brown. This step isn’t mandatory, but searing the chicken adds an extra layer of flavor.

Now, let’s bring it all together. In your slow cooker, layer the sautéed vegetables. Place the seared chicken on top, followed by the crushed tomatoes, balsamic vinegar, Italian herb blend, and, if you're feeling spicy, the crushed red pepper flakes. For those looking to counterbalance the acidity of the tomatoes, sprinkle in the sugar or honey.

Cover your slow cooker and set it to low for 6-8 hours or high for 3-4 hours. During this time, the chicken will cook to fork-tender perfection and the flavors will develop beautifully. If you're home while it’s cooking, take a moment to inhale that divine aroma!

Once cooking time is up, shred the chicken in the sauce with two forks. The meat should just fall apart. Give it a good stir to combine everything, and you’re ready to serve!