Preheat your oven to 400°F (200°C): Preparing the oven so it's hot when the ingredients are added will ensure even cooking. Grease a large baking dish to prevent sticking.
Season the chicken breasts: In a small bowl, combine 2 tbsp olive oil, 2 tsp garlic powder, 1 tsp oregano, 1 tsp paprika, salt, and pepper. Rub this mixture thoroughly over the 4 boneless, skinless chicken breasts, ensuring they are well-coated for maximum flavor.
Prepare the vegetables: In another bowl, toss the 3 cups of quartered baby potatoes and 2 cups of fresh green beans with the remaining 2 tbsp olive oil, 2 minced garlic cloves, 1 tsp dried thyme, 1 tsp smoked paprika, and season with salt and pepper until evenly coated.
Arrange the vegetables: Spread the seasoned potatoes and green beans evenly in the greased baking dish, creating a lovely bed for the chicken to rest on.
Nestle the chicken in: Place the seasoned chicken breasts on top of the vegetables, making sure they are spread out for even cooking.
Make the sauce: In a small bowl, whisk together the 1/4 cup chicken broth, juice of 1 lemon, and 1 tbsp Dijon mustard, ensuring it's well combined. Drizzle this sauce generously over the chicken and vegetables.
Roast and serve: Place in the preheated oven and roast for 40-45 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the potatoes are tender. Once cooked, allow everything to rest for about 5 minutes. Slice the chicken, serve alongside the veggies, and drizzle any remaining sauce on top for an extra burst of flavor!