Seared Tuna with Spinach and Root Vegetables

Name: Seared Tuna with Spinach and Root Vegetables
Ingredients: 2 tablespoons canola oil; 1 medium carrot, thinly sliced; 1 medium parsnip, thinly sliced; 1 small onion, thinly sliced; 1/4 cup water; 1 tablespoon unsalted butter; Salt and freshly ground pepper; 1 tablespoon mirin; 1 1/2 teaspoons low-sodium soy sauce; Pinch of ground Szechuan peppercorns; 1 pound tuna steak (about 1 1/4 inches thick); 1 garlic clove, thinly sliced; One 5-ounce bag baby spinach; 1 tablespoon chopped flat-leaf parsley