Tip:If you can’t find turkey cutlets, buy a boneless turkey breast and cut it on the diagonal into 1/4-inch slices.
Season the turkey with salt and pepper. Heat 2 Tbs. of the oil in a large skillet over medium high heat. When it’s hot, brown the turkey (working in batches so the turkey is evenly spaced) until it’s cooked through, 1 to 2 minutes per side. Transfer the cooked turkey to a wide plate and cover loosely with foil. Reduce the heat to low and add 1 Tbs. olive oil. Add the shallot and sauté, stirring frequently, until it softens slightly, about 3 minutes. Add 1/2 tsp. of the garlic and sauté, stirring, another 30 seconds. Increase the heat to high, add the broth and cook until it reduces by half, about 5 minutes. Add the cream and mustard and cook 1 to 2 minutes, whisking until thickened. Season with salt and pepper to taste; set aside.
Heat the remaining 1 Tbs. oil in another large skillet over medium-high heat. When it’s hot, add the remaining 1/2 tsp. garlic. Sauté for 15 seconds, shaking the pan so the garlic doesn’t burn. Add the spinach and cover the pan. Cook, stirring occasionally, until the spinach wilts completely, about 2 minutes. Toss with the lemon juice and remove from the heat.
Serve immediately, putting some spinach in the middle of each plate, topped with a portion of the turkey, a spoonful of the sauce, and a sprinkling of parsley.