Panfried stuffed tofu with fresh tomato sauce

Name: Panfried stuffed tofu with fresh tomato sauce
Ingredients: 200 g ground pork; 1 spring onion, white and green parts, finely chopped; 2 shiitake mushrooms, stemmed and finely chopped; 1 egg, lightly beaten; 1 tbsp fish sauce; 1/4 tsp black pepper; 1 tsp cornstarch dissolved in 2 tsp water; 1 large block regular or medium firm tofu (500 g); Canola oil for panfrying; 2 garlic cloves, minced; 1 1/2 cups peeled, seeded, and finely chopped ripe tomato; 1/4 cup water; 1 tsp fish sauce; Salt and sugar