Preheat Oven: Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly grease with oil.
Prepare the Honey Mustard Glaze: In a bowl, whisk together Dijon mustard, whole-grain mustard, honey, olive oil, garlic, vinegar (or lemon juice), paprika, salt, and pepper until smooth.
Season the Chicken: Place chicken breasts on the prepared baking sheet. Pat dry with paper towels and season lightly with salt and pepper. Brush generously with the honey mustard glaze, reserving 2–3 tbsp for serving.
Prepare the Carrots: Toss carrots with olive oil, honey, thyme, salt, and pepper. Spread carrots evenly around the chicken on the baking sheet.
Roast: Roast in the preheated oven for 25–30 minutes, or until chicken reaches an internal temperature of 165°F (74°C) and carrots are tender with golden edges.
Rest and Serve: Let chicken rest for 5 minutes before slicing. Drizzle with reserved glaze and garnish with fresh parsley and lemon wedges.