Season the chicken breast evenly with sea salt and black pepper.
Heat olive oil in a large skillet over medium-high heat and sear the chicken until golden brown and cooked through, then remove and set aside.
In the same skillet, add sliced mushrooms and minced shallots, sautéing until the mushrooms are browned and tender.
Stir in the minced garlic and cook for 30 seconds until fragrant.
Pour in the Marsala wine to deglaze the pan, scraping up any browned bits from the bottom.
Whisk the arrowroot powder into the chicken broth until smooth, then pour into the skillet and simmer until the sauce thickens into a silky glaze.
Return the chicken to the skillet, tossing to coat thoroughly in the mushroom sauce.
Serve the chicken and mushrooms over the warm linguine and garnish with chopped fresh parsley.