Warm the olive oil in a spacious skillet over medium heat.
Add the chopped garlic and crushed red pepper (if using) and sauté for about a minute.
Introduce the shrimp to the skillet, seasoning with salt and pepper, and cook for 2-3 minutes until pink and opaque.
Carefully incorporate the lump crab meat and chopped spinach, cooking for another 2-3 minutes until the spinach wilts.
Pour in the lemon juice and zest, followed by the heavy whipping cream, stirring gently.
Allow the mixture to reach a gentle simmer.
Gradually add the grated Parmesan cheese, stirring until it melts and integrates smoothly.
Taste and adjust seasoning with additional salt and pepper if necessary.
Remove from heat and sprinkle with fresh parsley before serving.