Cook the spaghetti in a large pot of salted boiling water until al dente, about 8–10 minutes. Reserve 1/2 cup of pasta water before draining.

Season the shrimp with salt and pepper In a large skillet, heat the olive oil and 2 tablespoons of the butter over medium-high heat. Add the shrimp in a single layer, and cook for 1–2 minutes per side, until pink and just cooked through. Remove shrimp and set aside.

Make the sauce: In the same skillet, reduce heat to medium. Add the remaining 2 tablespoons butter and garlic. Sauté for 1 minute until fragrant. Stir in red pepper flakes (if using), then add white wine. Simmer for 2–3 minutes to reduce slightly. Then add the chicken stock, lemon juice, capers, 2 to 3 lemon slices and reserved pasta water, simmer until sauce thickens (5-7 minutes) then remove the lemon slices

Combine and toss: Return shrimp to the pan, and toss in the cooked spaghetti. Add more reserved pasta water a little at a time to loosen the sauce, if the sauce is too tight.

Serve: Sprinkle with parsley, adjust seasoning, and serve hot with grated Parmesan and fresh lemon wedges if desired