Boil pasta shells in a large pot of salted water according to package instructions until al dente; drain and set aside.
Heat olive oil and 1 tablespoon of butter in a large skillet over medium-high heat.
Season shrimp with salt and pepper, then sear in the skillet for 2 minutes per side until pink and opaque; remove shrimp and set aside.
Add the remaining tablespoon of butter to the same skillet and sauté mushrooms until browned and moisture has evaporated, approximately 6 minutes.
Add minced garlic and red pepper flakes to the mushrooms and cook for 1 minute until fragrant.
Pour in the heavy cream and bring to a gentle simmer over medium heat.
Whisk in the Parmesan cheese until melted and the sauce begins to thicken slightly.
Add the fresh baby spinach to the sauce and stir until just wilted.
Return the cooked shrimp and pasta shells to the skillet, tossing gently to ensure even coating in the cream sauce.
Garnish with chopped parsley and serve immediately.