Steakhouse Dinner on the Grill

Name: Steakhouse Dinner on the Grill
Ingredients: 6 cloves garlic, peeled; One 2-pound London broil steak (1 1/2 to 2 inches thick); 1/2 cup extra-virgin olive oil; 1/4 cup red wine vinegar; 1/4 cup fresh basil, chopped; 1/2 teaspoon red pepper flakes; 1/4 cup plus 1 teaspoon Worcestershire sauce; Kosher salt and freshly ground black pepper; 8 tablespoons unsalted butter, at room temperature; 1 shallot, finely chopped; 1/2 cup fresh parsley, chopped; 2 tablespoons chopped fresh chives; 2 pounds red creamer potatoes, quartered or halved into 1-inch pieces; 1 pound baby spinach