Preheat your grill to high or your oven to 425°F.
Slice the chicken breasts into 4 pieces, making sure they’re even. Pound them lightly to ensure they are about 4 ounces each.
In a large bowl, combine the chicken, baby potatoes, bell pepper, onion, carrot, and minced garlic. Drizzle with olive oil and sprinkle all the seasonings on top. Don't forget to add salt and pepper—about 1 teaspoon of salt and 1/4 teaspoon of pepper for balance. Toss everything well to coat.
Now, lay out 4 large sheets of foil. Evenly divide the mixture between the sheets, ensuring each packet gets a piece of chicken on top.
Top each packet with 1 tablespoon of butter. Seal each foil packet tightly, making sure no steam can escape.
Cook on the grill for about 15 to 25 minutes (my sweet spot is around 20 minutes). If using the oven, bake for 30 to 45 minutes, until the chicken registers an internal temperature of 165°F.
Carefully open the foil packets to release the steam—be cautious! Add a drizzle of olive oil, some chopped parsley, and a squeeze of lemon juice on top of the cooked veggies and chicken.
For a stovetop option, heat 2 tablespoons of oil in a large skillet. Add the chicken in a single layer and cook for 2 to 4 minutes on each side. After flipping, add 1 tablespoon of butter. Cook until fully cooked through, then transfer to a plate and cover with foil to keep warm.
In the same skillet, add more oil if needed, along with another tablespoon of butter. Cook all the veggies until crisp-tender, stirring occasionally. Plate the chicken and veggies together, topping with Parmesan and fresh lemon juice to finish.