Place a large skillet over medium heat and add 2 tablespoons of the oil. Once shimmering, add the patties in a single layer, making sure they all have complete contact with the bottom of the pan. If they don’t all fit at once, cook in batches. Sauté for 3 – 4 minutes on each side, until golden brown and crispy. Transfer chicken to a plate and cover with foil to keep warm.
Return the skillet to the stove and add the remaining oil. Add the shallot, garlic, and mushrooms, stirring well. Cook for 2 – 3 minutes, until softened and aromatic, being careful not to burn the vegetables. Slowly pour in about half of the vegetable stock, pausing to scrape the bottom of the skillet with your spatula, incorporating all the flavorful browned bits that might be sticking.
To the remainder of the vegetable stock, add the Dijon mustard, lemon juice, and cornstarch. Whisk vigorously to combine before pouring the liquid mixture into the skillet. Turn down the heat to medium-low and let simmer gently for about 5 minutes. Once the sauce has thickened, add the capers and season with pepper.
Either add the cooked patties back into the pan, tossing to coat, or keep the sauce separate to pour on top. Serve over hot, cooked pasta and sprinkle with fresh parsley.
Notes: Try using raw zucchini noodles or sweet potato spirals as a gluten-free alternative to conventional noodles.