Preheat oven to 425 degrees. Finely chop the walnuts or crush them with the bottom of glass. Scrub the potato and cut into 1/2-inch cubes (no need to peel!). Strip the rosemary leaves off the sprig and finely chop.

Toss the potatoes with half the rosemary, 1 table spoon olive oil, and a pinch of salt and pepper. Spread out on the baking sheet and roast for about 20 minutes, until cooked through and golden brown.

Place the chicken breast between two pieces of plastic wrap or in a large zip-top bag. With the mallet (or the bottom of a small pot), pound the chicken breasts until they are half their original thickness. Season the chicken on both sides with salt and pepper.

In a small bowl, combine the panko, crushed walnuts, remaining rosemary, and 1 table spoon olive oil. Season the mixture with salt and pepper.

Remove the baking sheet from the oven and make space for the chicken breasts. Place the chicken breasts on the baking sheet and coat the top with the Dijon mustard, the top with walnut-pinko mixture and press to adhere. Bake for 10-12 minutes, until the chicken is cooked through and the crust is golden and crispy.

Just before the chicken is done, toss the mixed greens with 1 tablespoon olive oil , 1/2 tablespoon balsamic vinegar, and a pic of salt and pepper in a medium bowl.

Serve the chicken with the roasted potatoes and salad to the side.