Bring a large pot of salted water to a rolling boil. Add the tortellini and cook according to package directions, typically 2-3 minutes for fresh or 5-7 minutes for frozen, until al dente. Drain, reserving about 1/2 cup of pasta water, and set aside.

While the tortellini cooks, pat the shrimp dry with paper towels. Season with 1/2 tsp salt and 1/4 tsp black pepper. Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add the shrimp in a single layer and cook for 1-2 minutes per side, until pink and opaque. Do not overcrowd the pan; cook in batches if necessary. Remove shrimp from the skillet and set aside.

Reduce the heat to medium. Add 2 tbsp butter to the same skillet. Once melted, add the minced garlic and sauté for 1 minute until fragrant, being careful not to burn it. Pour in the 1/2 cup dry white wine (or chicken broth) and scrape up any browned bits from the bottom of the pan with a wooden spoon. Let it simmer for 2-3 minutes until slightly reduced.

Stir in the 1.5 cups heavy cream. Bring to a gentle simmer and cook for 3-5 minutes, stirring occasionally, until the sauce thickens slightly. Reduce heat to low.

Add the 1/2 cup grated Parmesan cheese to the sauce and whisk until melted and smooth. Stir in the 4 cups fresh spinach, stirring until it wilts completely, about 1-2 minutes.

Return the cooked shrimp and drained tortellini to the skillet with the sauce. Add 1 tbsp fresh lemon juice. Toss gently to combine, ensuring everything is well coated. If the sauce is too thick, add a tablespoon or two of the reserved pasta water until it reaches your desired consistency.

Taste and adjust seasoning if needed. Garnish with additional grated Parmesan cheese and chopped fresh parsley, if desired. Serve immediately.