Preheat oven to 200°C (400°F) and line a large baking tray with parchment paper.

Place each chicken breast flat on a cutting board. Using a sharp knife, cut a deep horizontal pocket into the thickest part of each breast, being careful not to cut all the way through.

Season the inside of each pocket with a pinch of salt and pepper. Stuff each chicken breast with 30g of fontina cheese and 2 slices of prosciutto, folding them to fit inside.

Secure the openings with toothpicks if needed. Rub the outside of each chicken breast with 1 tablespoon of olive oil, then season with rosemary, thyme, salt, and pepper.

Toss the asparagus, snap peas, and baby carrots with remaining 2 tablespoons olive oil, minced garlic, lemon zest, salt, and pepper in a large bowl.

Arrange the stuffed chicken breasts in the center of the prepared baking tray and scatter the seasoned vegetables around them.

Roast in the preheated oven for 30-35 minutes, or until the chicken reaches an internal temperature of 74°C (165°F) when measured at the thickest part with a meat thermometer.

Remove from oven, drizzle lemon juice over the vegetables, and let the chicken rest for 5 minutes before removing toothpicks.

Garnish with fresh parsley and serve immediately with the roasted spring vegetables.