Lightly toast the muffins on the top side only using a broiler on high and laying muffins ½ sides on a sheet pan. Broil 2-3 minutes or until just lightly toasted.
Combine remaining ingredients in a food processor and pulse until everything is just combined. There should be some texture to the shrimp and water chestnut.
Spread liberally on English muffins ½ side and set broiler to low.