Preheat your oven to 400°F (200°C). Wash and halve the baby potatoes, then toss them in 1 tablespoon of olive oil, the fresh rosemary, salt, and pepper. Spread them out on a baking sheet in a single layer and roast for about 25-30 minutes, tossing halfway through.
While the potatoes roast, heat the remaining tablespoon of olive oil in your skillet over medium-high heat. Season the chicken breasts generously with salt, pepper, and dried rosemary. Add chicken to the hot pan and sear for 5-6 minutes per side until golden and cooked through. Remove and set aside.
In the same skillet, add minced garlic and sliced mushrooms. Sauté for 5-7 minutes until mushrooms are browned and garlic is fragrant, stirring frequently.
Lower the heat to medium and pour in the heavy cream. Stir well to combine with mushrooms and garlic. Let simmer gently for 3-5 minutes until the sauce thickens slightly. Adjust seasoning with salt and pepper.
Return the seared chicken breasts to the skillet, nestling them into the creamy mushroom sauce. Spoon sauce over chicken and warm together for a minute or two.
Serve the creamy mushroom chicken alongside the rosemary potatoes. Garnish with extra fresh rosemary if desired.
