Blend the onions and lemongrass in a blender or food processor with ¼ cup (60ml) of water. Mix in ground coriander, turmeric, chili powder, and sugar. Divide evenly between 2 large bowls.
Add beef and chicken into each of the bowls. Give it a good stir to get meat well coated with spices. Cover with plastic wrap and allow meat to marinate in refrigerator for at least an hour. It is best to marinade over night. The longer meat is marinated, the better the flavor.
Thread 5 pieces of marinated beef and chicken onto each skewer until all meat pieces are used up.
Grill skewered meats over barbecue grill brushing with oil for 6 to 7 minutes on each side**.
Turn the skewers frequently to prevent meat from burning. Meat should be slightly charred on the outside and just cooked on the inside.
Remove and serve immediately with Satay Peanut Sauce, sliced cucumber, and onions.
Notes
**Alternatively, satay can be cooked under the broiler for 8 to 9 minutes on each side.