Peanut oil has a high flash point and I like the flavor but you can use other oils. I found the dark soy sauce in Chinatown, you can mail order it from Amazon, too. Kim Lan is a favorite taiwanese soy sauce. I keep the meat finely chopped so the flavors blend easier.
This is a favorite Taiwanese dish that I used to get at St Alps Tea House on Bedford Ave. before they closed. Taiwanese Braised Pork Belly is also slightly similar to Shanghainese Red Braised Pork Belly (Chinese: 紅燒肉; Hong Shao Rou), Chinese Dongpo Pork (Chinese: 東坡肉), and Japanese Braised Pork Belly Kakuni (Japanese: 角煮).
Note: You can make your own five-spice powder by combining 1/4 teaspoon each ground cloves, Sichuan peppercorns, and fennel seed, plus 1 cinnamon stick and 1 clove star anise.