Season the chicken with oregano, salt, and pepper.
4 boneless skinless chicken breasts, 1 teaspoon oregano, 1 teaspoon kosher salt, 1/4 teaspoon black pepper
Place a large skillet over medium heat. Add the oil and heat. Cook the chicken for 8 minutes on each side. Remove from the skillet and tent loosely with foil.
2 tablespoons olive oil
In the same skillet, melt the butter. Add the garlic and sauté until fragrant, about 30 seconds. Add the tomatoes and cook until softened, about 3 minutes. Add the spinach and cook until it begins to wilt, about 2 minutes.
3 tablespoons unsalted butter, 4 garlic cloves, 1 1/2 cups cherry tomatoes, 5 cups baby spinach
Stir in the heavy cream and Parmesan cheese and bring to a simmer (you should have the heat low, but still see intermittent bubbles). Turn the heat to low and allow the sauce to thicken, about 5 minutes.
1 cup heavy cream, 1/2 cup Parmesan cheese
Return the chicken to the skillet (without the liquid it has accumulated) and cook for another 5 to 8 minutes, until it is cooked through. Taste the sauce and add more salt and pepper to taste.