For the breading: In a small bowl, blend the panko and coconut and hold at room temperature until breading. For the sauce: In a medium saucepan over medium-high heat, cook the mangos with 1/4 cup cold water and the sugar until the mangos have started to break down, stirring throughout. This should take 10 to 12 minutes. Next, add the Sriracha and continue to cook for 5 minutes. Remove from the heat and puree in a food processor or blender. Then add the horseradish. Serve or hold.
For the batter: In a medium mixing bowl, blend the lager, flour, baking powder, Cajun spice and egg yolk with a whisk; the batter should be thick like pancake batter consistency. If additional flour or liquid is needed, add and whisk again and hold cold until breading.
For the shrimp: Heat the oil in a deep-fryer to 325 degrees F. Season the flour with salt and pepper. Lightly coat the shrimp, excluding the tails, with the seasoned flour, then dip in the beer batter. Evenly coat with the coconut breading, and repeat the process until all the shrimp have been dressed.
Carefully place the shrimp in the fryer and cook until golden brown. Repeat the process until all the shrimp have been cooked. Serve with the mango sauce.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.