Canned luncheon meat (Spam)
Cured, cooked pork pressed into a firm block and canned; salty and fatty, usually sliced and pan-fried.
The style common in Korea is sold in Asian grocery stores and most ordinary supermarkets; German-style Frühstücksfleisch is related but usually leaner and milder.
Substitute:
Supermarket luncheon meat or thick-cut cooked ham will do, but they brown less crisply and give stews less salt and fat, so season a little more.