Place the Brie in the freezer for 15 minutes while you prepare the coating.
Add the pistachios to the bowl of a food processor and blend until finely ground. (Alternately, add the pistachios to a sealable plastic bag and crush until finely ground.)
In a medium bowl, stir together the ground pistachios and Panko breadcrumbs.
In a separate medium bowl, add the flour.
In a third medium bowl, whisk the egg with 2 tablespoons water.
Dredge the Brie in the flour, shaking off an excess. Dip the Brie in the eggs then coat it all over with the pistachio mixture.
Add 1/2-inch oil to a large skillet set over medium-high heat. Line a plate with paper towels.
Once the oil reaches 300°F on an instant-read thermometer, add the Brie and cook until golden brown on one side, about 2 minutes. Flip it once and continue cooking an additional 1 to 2 minutes. Using a spatula (the Brie will be very gooey inside), transfer it onto the paper towel-lined plate. Let it rest for 5 minutes before drizzling with honey and serving with crackers.