Thinly slice only the pale portion of the lemongrass. Place in food processor or blender.
Add ground coriander, ground cumin, turmeric, galangal, brown sugar, salt, shallots, garlic, soy sauce, cooking oil and water into the food processor or blender.
Blend until smooth.
Pour marinade over chicken. Gently massage the marinade into the chicken (don't forget to wear disposable gloves!)
Allow the chicken to marinade in the fridge for at least 2 hours, up to overnight.
Grill or pan-fry for about 2 minutes on each side or until fully cooked.
Place grilled satay chicken on the bottom hamburger bun.
Top with sliced red onion and sliced cucumber.
Smear spicy peanut sauce on the top hamburger bun, then place it on the rest of the burger.
Serve with fries, potato chips or shrimp crackers.