Heat the oil in a skillet over medium-high heat. Season the chicken with salt and pepper to taste, then add to the heated skillet.

Sauté the chicken until cooked through, then remove and set aside to keep warm.

Melt the butter in the skillet over medium heat. Add the onions and sauté until they start to become tender.

Add the garlic, dried sage, and fresh parsley. Sauté another 30 seconds.

Pour in the cooking wine and continue cooking until the liquid is reduced by half.

Whisk in the heavy whipping cream. Continue to simmer until the sauce starts to thicken.

Add the spinach to the skillet.

Cover with a lid and cook until the spinach is wilted.

Transfer the chicken back into the skillet.

Stir until the chicken is well-coated, then remove from heat and serve.