Heat some cooking oil in a pan over medium-high heat. Once it’s hot, add garlic and ginger, and cook for about 2 minutes.
Toss in the tomato and onion, and cook until they soften. Then, add the canned corned beef and cook for 2 minutes.
Add sinigang mix powder (don’t overdo it yet—you can always adjust the seasoning later), the white part of pechay (if using pechay), radish, chilis, and water. Cover the pan and let it cook for about 5 minutes. Check the radish if cooked after 5 minutes.
Stir in the eggplant slices. Cover again and cook for another 2 minutes.