Preheat the oven to 425°F and line a large baking sheet with parchment paper.
In a bowl, toss halved baby potatoes with 2 tablespoons olive oil, 1 teaspoon garlic powder, rosemary or thyme, salt, and black pepper.
Arrange the potatoes in a single layer on the prepared baking sheet and roast for 25 to 30 minutes, turning once halfway, until golden and crisp.
Season chicken breasts with salt, black pepper, and the remaining 1 teaspoon garlic powder.
Heat 1 tablespoon olive oil in a large skillet over medium-high heat and sear chicken breasts for 4 to 5 minutes per side until golden and cooked through, then transfer to a plate.
Reduce heat to medium and add minced garlic to the skillet; sauté for 1 minute until fragrant.
Pour in chicken broth, stirring and scraping any browned bits off the pan, and simmer for 2 to 3 minutes.
Add heavy cream, grated Parmesan, Dijon mustard, and Italian seasoning to the skillet, stirring well. Simmer for 3 to 5 minutes to thicken the sauce slightly.
Return the chicken breasts to the skillet, spoon sauce over them, and simmer for 2 to 3 minutes until heated through.
Serve the creamy garlic chicken hot with roasted baby potatoes, garnished with fresh parsley if desired.