Pat the chicken breast dry with a paper towel and season both sides evenly with sea salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Place the chicken in the skillet and sear for 5 to 7 minutes per side, or until the internal temperature reaches 165 degrees Fahrenheit.
While the chicken is cooking, place the pre-cooked potato on a clean surface and gently press down with a fork to flatten it into a thick disc.
Remove the chicken from the skillet and let it rest on a cutting board.
In the same skillet, add the smashed potato, minced garlic, and fresh rosemary, using the residual oil to crisp the potato for 3 minutes per side until golden.
Meanwhile, steam the green beans in a small amount of water for 4 minutes until they are bright green and tender-crisp.
Slice the chicken and serve it alongside the crispy potatoes and green beans, finishing the dish with a fresh squeeze of lemon juice.