Gather all ingredients and equipment together. Do the necessary chopping and measuring so all is ready to go.
Heat a large skillet over medium-high heat. Add spinach; cook and stir until wilted.
Drain the spinach in a sieve set in a bowl to catch the liquid. Press out as much of the liquid as possible. Set aside.
Add the butter and onion to the skillet over medium heat. Cook for about 5 minutes, stirring occasionally, until tender.
Add the garlic, salt, and pepper, and cook for a minute.
Add the drained spinach back into the skillet and stir well to combine.
Stir in the half and half. Let it heat through.
Add the provolone cheese in small pieces to the spinach mixture. Stir until cheese is melted.
Stir in the Parmesan cheese. Continue to cook and stir until desired thickness.
Serve hot.
