Slow Cooker Cincinnati Chili

Name: Slow Cooker Cincinnati Chili
Ingredients: 1 small white onion; 3 cloves garlic; 1 tablespoon olive oil; 2 teaspoons kosher salt, divided; 1 teaspoon freshly ground black pepper, divided; 1 1/2 pounds lean ground beef; 1 (2.25-ounce) packet Cincinnati Chili Spice; 1 (15-ounce) can tomato sauce; 1 cup water; 2 teaspoons unsweetened cocoa powder; 1 pound cooked spaghetti, for serving (optional); Garnish options: 2 cups finely grated cheddar cheese, 1/2 cup raw diced white onion, and hot sauce