Seared Steak & Creamy Cajun Shrimp with Sautéed Spinach & Mashed Yukon Potatoes

For the Creamy Cajun Shrimp:

 1/2 lb shrimp, peeled and deveined
 1 tablespoon Cajun seasoning
 1/2 teaspoon salt
 2 tablespoons unsalted butter
 2 cloves garlic, minced
 1/2 cup heavy cream
 1/4 cup grated Parmesan cheese
For the Sautéed Spinach:

 4 cups fresh spinach
 1 tablespoon unsalted butter
 1 clove garlic, minced
 Salt and black pepper to taste