Kale and Mushroom Croquetas

In a large sauté pan over medium-high heat, warm the olive oil. Add the mushrooms, add a pinch of salt and sauté until the mushrooms are well browned and any liquid has evaporated, 5 to 7 minutes. Add 1 Tbs. of the butter and cook until the butter foams. Add the onion and garlic and continue cooking, stirring frequently, until the onion has softened slightly, about 3 minutes. Add the kale and continue to cook, stirring frequently, until the kale is wilted, about 3 minutes. Add the 2 tsp. vinegar and stir to scrape up any browned bits from the bottom of the pan. Remove the pan from the heat, season with salt, and stir in a bit more vinegar, if desired. Set aside and let cool to room temperature.

Transfer the vegetable mixture to a food processor and process until very finely chopped, about 30 seconds. Transfer to a bowl and set aside.

In a sauté pan over medium-low heat, combine the remaining 8 Tbs. (1 stick) (4 oz./125 g) butter and the 2/3 cup (3 1/2 oz./105 g) flour. Cook until the butter has melted and the mixture is uniform and a light golden color, 3 to 5 minutes. Slowly whisk the milk into the roux to create a thick sauce. Whisk in the nutmeg and season with salt. Remove the pan from the heat stir in the vegetable mixture until well combined. Transfer the mixture to a bowl and cover with plastic wrap, pressing the wrap directly onto the surface of the mixture. Refrigerate until cold, at least 2 hours and up to overnight.

Line a baking sheet with parchment paper.

Place the remaining 1 1/2 cups (7 1/2 oz./235 g) flour in a shallow bowl. In a separate shallow bowl, whisk the eggs with a fork to blend. Put the panko in a food processor and pulse several times until they are finely ground. Transfer the panko to a separate shallow bowl.

Using a tablespoon or a 3/4-ounce (20-g) scoop, form the mushroom mixture into 1 1/2-inch (4-cm) balls. As they are formed, roll the balls in the flour, then the eggs and then the panko to coat. Transfer to the prepared baking sheet as they are done.

Fill a large pot or Dutch oven about halfway with vegetable oil and heat to 350°F (180°C) on a deep-frying thermometer. In batches to avoid crowding, carefully place the croquetas in the hot oil and cook, turning as needed, until golden brown, 2 to 3 minutes per batch. Using a slotted spoon, transfer the croquetas to a wire rack placed over a baking sheet to drain. Keep warm until all the croquetas are cooked.

Arrange on a platter, season with salt and serve hot. Makes about 40 croquetas; serves 8.

Ryan Pollnow, chef, Aatxe, San Francisco, CA