In a large pot or Dutch oven, heat the 2 tablespoons of salted butter and 1 tablespoon of olive oil over medium heat. Once the butter is melted, add the minced shallot and sauté for about 2-3 minutes until translucent. Stir in the minced garlic and lemon zest, cooking for an additional minute until fragrant.
Add the uncooked orzo pasta to the pot, stirring it into the aromatic mixture. Allow the orzo to toast for about 1-2 minutes, which will enhance its nutty flavor. Then, pour in the 2 1/2 cups of vegetable or chicken broth. Increase the heat to bring the mixture to a boil, then reduce to a simmer. Cover and cook for 8-10 minutes, or until the orzo is al dente and has absorbed most of the liquid.
Once the orzo is cooked, stir in the 2 cups of chopped fresh spinach and mix until wilted. Then, pour in the 1/2 cup of heavy cream and the 1/2 cup of grated Parmesan cheese. Mix everything together until the cheese has melted and the sauce is creamy. Season with kosher salt and black pepper to taste.
Ladle the creamy orzo into bowls and garnish with crushed red pepper flakes, fresh basil, and extra Parmesan cheese, if desired. Serve with lemon wedges on the side for a refreshing zest that balances the creaminess.