Shanghai fish head and tofu soup

Ingredients

• 1 large fish head (carp or sea bass, about 500 g)
• 300 g soft tofu (cut into cubes)
• 100 g white radish (sliced)
• 3 slices ginger
• 2 scallions
• 1 tbsp Shaoxing wine
• 1 tbsp vegetable oil
• 1 tsp salt, white pepper to taste
• 1.5L water