Clean the freshwater crabs, remove the shells, and set the crab roe aside in a separate bowl.

Grind the crab bodies, then strain to remove the solids. Add a pinch of salt to the crab liquid in a pot. Gently stir over medium heat in one direction to prevent sticking. When the crab forms clumps and floats, skim them out. Add some onion, ginger, onion, pineapple, and pork bones to the broth and simmer on the stove. (If you like a sour taste, you can add a little fermented rice or tamarind.)

For the crab mixture, if you prefer it soft, leave it as is. If you like it firmer, add an egg, a little seasoning powder, and ground pork, mix well, then steam until cooked and cut into pieces.

Sauté onion until fragrant, add tomatoes and crab roe, and cook until done. Cut the tofu into pieces and fry until golden.