Ingredients
5tbspunsalted butter
2leeks
¼lbshiitake mushrooms
salt
freshly ground pepper
1tspthyme,chopped
1tsporegano,chopped
3tbspall purpose flour
1cupmilk
½cupgruyère,shredded
¼cupparmigiano-reggiano,freshly grated
2large eggs
1½cupspanko
vegetable oil
Preparation
In a large skillet, melt 2 tablespoons of the butter. Add the leeks and shiitake, season with salt and pepper, and cook over high heat, stirring frequently, until the leeks and mushrooms are softened and beginning to brown.
Add the thyme and oregano to the vegetables and transfer to a medium bowl. In a small saucepan, melt the remaining 3 tablespoons of butter. Whisk in the 3 tablespoons of flour and cook over high heat until bubbling for about 1 minute.
Add the milk and cook, whisking, until very thick and bubbling, for about 3 minutes. Scrape the mixture into the bowl. Add the Gruyère and Parmigiano-Reggiano, season with salt and pepper, and stir until the mixture is evenly combined.
Lay an 18-inch-long piece of plastic wrap on a work surface. Spoon the croquette mixture onto the plastic in a 12-inch strip. Roll up the plastic, pressing the croquette mixture into a 14-inch log, and twist the ends.
Freeze the croquette log until very firm. This will take about 2 hours. Fill 3 shallow bowls with flour, the beaten eggs, and the panko and line a large baking sheet with wax paper.
Unwrap the log and cut the croquette mixture into 12 pieces. Using floured hands, pat each piece into a 2-inch round patty, about ¾ inch thick.
Dip each patty in the flour, then dip in the eggs and coat with panko, pressing to help it adhere. Set the croquettes on the baking sheet and freeze for 15 minutes.
In a large skillet, heat half an inch of oil to 375 degrees F. Add all of the croquettes and fry over high heat, turning once or twice, until they are golden and crisp, for about 5 minutes. Drain on paper towels and serve hot.
