Directions For the Sauce:
For the sauce, add the Grand Marnier and orange juice together in a sauce pan and cook over medium heat for about 20 minutes to reduce to a syrupy consistency. Cool immediately*. Combine the reduction and pulsed orange zest powder with the mayonnaise and refrigerate.
Directions For the Prawns:
To cook the prawns, heat canola oil or frying oil to 350 degrees.** Dust the prawns in the cornstarch, shaking off any excess starch. Fry the prawns until crispy (about 2 minutes) and drain on paper towels. In a large bowl, toss the hot prawns in the Grand Marnier mayonnaise to coat.
*To cool the sauce quickly, rather than refrigerating it, spoon it into a bowl set inside a larger bowl filled with ice and water.
**If you don't have a food thermometer to measure the temperature of the oil, heat it over medium until it is below the smoke point — don't let it smoke. The shrimp should sizzle when they hit the oil and the oil should bubble while they cook. Don't overcook the shrimp—a minute on each side should cook them through and leave a little crispy crust on the outside.