Spicy Roasted Cauliflower Stir-Fry

Ingredients

• 1 large head cauliflower, cut into florets
• 4 tablespoons vegetable oil, divided
• Salt
• Freshly ground black pepper
• 6 (1/4-inch thick) slices fresh ginger
• 1 small onion, thinly sliced
• 5 cloves garlic, thinly sliced
• 2 medium scallions, cut crosswise into 2-inch lengths
• 2 tablespoons Shaoxing rice wine or dry sherry
• 1 1/2 tablespoons tamari or soy sauce
• 1 teaspoon toasted (Asian) sesame oil
• 1/2 teaspoon red pepper flakes (optional)
• 1/4 teaspoon granulated sugar
• Steamed rice, for serving (optional)