Step 1

Season the chicken with the salt and a few grinds of pepper. Spread the flour on a plate. Coat the chicken in the flour and set on another plate. Reserve the flour.

Step 2

Heat a large skillet over medium-high heat. Add 2 tablespoons each butter and olive oil; let melt. Working in batches, cook the chicken until browned, 1 to 2 minutes per side. Remove to a clean plate.

Step 3

Wipe the skillet clean with a paper towel and return to medium-high heat. Add another tablespoon each of butter and olive oil. When the butter melts, add the mushrooms and season with salt and pepper. Cook, stirring, 3 to 4 minutes.

Step 4

Reduce the heat to medium. Add 1 more tablespoon olive oil, the shallots and sage and cook, stirring, 3 to 4 minutes. Sprinkle with 1 tablespoon of the reserved flour and toss to coat. Add the Marsala, bring to a simmer and cook until reduced by half, 1 to 2 minutes. Add the chicken broth; return to a simmer. Cook until slightly thickened, 2 to 3 minutes.

Step 5

Add the chicken and half of the parsley to the skillet. Simmer until the chicken is cooked through, about 2 minutes.

Step 6

Meanwhile, bring a large pot of salted water to a boil. Add the spaghetti and cook as the label directs for al dente. Reserve ½ cup cooking water, then drain the spaghetti and transfer to a bowl. Add the remaining 3 tablespoons butter and 2 tablespoons olive oil and the remaining parsley; season with salt and pepper. Add ¼ cup of the reserved cooking water and toss, adding more cooking water if needed. Serve with the chicken and sauce.