After testing many versions of this dish, we came back to this one, from one of our favorite books, Pacific and Southeast Asian Cooking(Time-Life Books, 1970).
FOR THE KECAP MANIS:
3/4 cup Japanese soy sauce
3 tbsp. molasses
1/2 tsp. ground laos (ground galangal)
1/2 tsp. ground coriander
1/2 tsp. freshly ground black pepper
FOR THE SATE:
2 cloves garlic, peeled and minced
1 tsp. salt
2 pinches freshly ground white pepper
2 tbsp. kecap manis, (see above)
Juice of 1 lime
2 whole boneless, skinless chicken breasts,
cut into 1'' x 3'' strips, or 5 boneless, skinless
chicken thighs, cut into 1'' cubes
FOR THE PEANUT SAUCE:
2 tbsp. vegetable oil
2 small shallots, peeled and finely chopped
1 large clove garlic, peeled and minced
1/4 tsp. shrimp paste
2 cups chicken stock
1/2 cup unsalted roasted peanuts, preferably
Spanish peanuts, ground to a paste
1 tbsp. kecap manis (see above)
1/4 tsp. grated ginger
2 red Thai chiles, stemmed and finely chopped
1/2 tsp. dark brown sugar
Juice of half a lime
**FOR THE SAMBAL KECAP:
4 red Thai chiles, stemmed
1 cup kecap manis (see above)
1/4 cup lime juice
1. For the kecap manis: Bring sugar and 1 cup water to a boil in a medium saucepan over medium-high heat, stirring until sugar dissolves, about 3 minutes. Continue boiling until syrup reaches 200° on a candy thermometer, about 1 minute. Reduce heat to medium, stir in soy sauce, molasses, laos, coriander, and pepper, and simmer until very thick and reduced by a third, about 40 minutes. Set aside.
2. For the sate: Put garlic, salt, and pepper in a large bowl and mash into a paste with the back of a wooden spoon. Stir in kecap manis and lime juice, add chicken, and toss until well coated. Cover, refrigerate, and allow to marinate for 2 hours.
3. For the peanut sauce: Heat oil in a heavy medium pan over medium heat. Add shallots and garlic and cook until soft, about 3 minutes. Stir in shrimp paste, mashing with the back of a spoon, and cook for 1 minute. Add stock, bring to a boil, then stir in ground peanuts, kecap manis, ginger, chiles, and sugar, and simmer, stirring often, until sauce thickens to a loose paste, about 20 minutes. Keep sauce warm over low heat, adding lime juice just before serving. (Add a little water to thin sauce, if necessary.) Transfer sauce to a serving bowl.
4. For the sambal kecap: Slice chiles crosswise into thin rings and put into a small serving bowl. Add kecap manis and lime juice, mix well, and set aside.
5. Preheat grill. Remove chicken from marinade and thread each piece of breast or several pieces of thigh onto about sixteen 6''-long bamboo skewers. Grill chicken over hot coals, turning to brown on both sides, until chicken is cooked through, 3-5 minutes. Serve with warm peanut sauce and sambal kecap.