Clean the chicken breasts, pat dry with a clean kitchen cloth, and dice them into bite-sized chunks.
Season the chicken with salt and lemon pepper; set aside for 10 minutes. Meanwhile, finely mince or chop garlic and slice mushrooms as desired.
Heat olive oil in a medium-sized cast iron pan or skillet over medium heat. Add chicken breast and brown it for about 4 minutes on each side, avoiding stirring too early to achieve a golden color. Then, remove the chicken and set it aside on a plate.
Reduce the heat to low, add garlic to the pan, and fry until slightly browned and soft. Then, pour in the chicken stock, raise the heat to medium, and stir. Finally, add in the mushrooms.
To make the mascarpone sauce, mix in mascarpone cheese and simmer for 5 minutes. Return the chicken breast to the pan, reduce heat to low, adjust salt if necessary, cover, and simmer for 10 minutes. Optionally garnish with basil, thyme, or other herbs.
Serve with cauliflower mash, zoodles, or a side dish of your choice such as pasta, or mashed potatoes.