Begin by making galette dough. Whisk egg yolk and vinegar together in a small cup or bowl and add ice water. In a food processor, pulse flour, salt and butter until a course, crumbly meal forms. Add liquid and quickly run processor just until a ball of dough forms. Immediately stop processor, remove dough and flatten into a disk. Wrap dough in plastic wrap and refrigerate at least 30 minutes or until ready to use.
Preheat oven to 350 degrees F. Put rockfish on a lightly greased sheet pan and season with lemon zest, lemon juice, salt and crab boil seasoning, to taste. Roast until fish is firm to the touch and flakes easily, about 15 to 20 minutes depending on thickness of fillets. Set aside.
Remove galette dough from refrigerator, lightly dust with flour and roll out to 1/4 to 1/2 inch thick. Using a 1 1/2 to 2" cookie cutter, or a lightly floured glass, cut dough into circles and put on a lightly greased baking sheet. Score each circle with the tines of a fork and bake for 10-12 minutes, or until golden brown. If the galettes are puffing up too much, put a second, ungreased cookie sheet on top of the first to weight the dough down slightly.
Remove galettes from oven and top with warm flaked rockfish, truffle oil and chives (if using). Serve immediately.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.