Combine all the ingredients except the lamb in a food processor or blender. Blend until smooth. Taste and adjust the seasonings - adding more jalapeno if a spicier marinade is desired.
Place the lamb in a large ziploc bag and pour enough marinade over to completely coat the lamb - refrigerate the lamb for 8 hours or overnight.
You may have extra marinade. Refrigerate and use within a day.
Soak ten 12 inch wooden skewers in warm water for 30 minutes. Thread each skewer with 6 to 7 chunks of lamb until all the lamb is used. Pour reserved marinade into a small saucepan and bring to a boil. Reduce the heat and simmer for 5 minutes. Let cool.
Pre heat your grill to medium high heat. Add the lamb and cook, turning occasionally, until the lamb is cooked and slightly pink in the middle - about 7 - 8 minutes total. Use a thermometer to check the internal temperature of 140 for medium - 130 degrees if you like it rare!