Heat a large skillet over medium high heat and add 1 tbsp of olive oil.
Butterfly the chicken breasts and season with salt and pepper. Add the breasts to the hot skillet and saute on both sides until cooked through, about 4 minutes per side. Chicken should be light golden brown.
Remove the chicken from the pan and set aside on a plate.
Add the garlic, butter, and red onion to the pan. Cook until fragrant, 1-2 minutes.
Add the wine to the skillet (feel free to substitute with broth). Let it simmer and reduce 2-3 minutes. Add the spinach to the skillet and cook until wilted, about 1 minute.
Reduce the heat to medium low and add heavy cream. Stir using a wooden spoon. If desired, add additional salt and pepper to taste.
Transfer the cooked chicken breasts to the skillet and simmer for 2-3 minutes until heated through. Flip the chicken in the sauce to coat. Serve immediately.
Best stored in a air tight container in the fridge up to 5 days.