Courtesy Chef Hubert Keller
You might call it a trompe l'oeil burger, but there is nothing tricky about its flavors. Rich chocolate ganache forms the burger. A mango gel&eacute;e masquerades as American cheese. Under the sweet bun, you will discover whipped cream "mayonnaise," fresh mint "lettuce," kiwi "pickles," and strawberry sauce "ketchup." Build your own: The recipe may look labor-intensive, but all the pieces can be completed well ahead and then assembled at serving time. The chocolate burger recipe may be doubled and keeps, covered and refrigerated, for 1 week. You can also shape the mixture with a melon baller into small, round truffles and roll them in cocoa powder, ground nuts, or shredded coconut.
1 cup unsweetened mango pur&eacute;e
2 to 6 tablespoons sugar, to taste
2 tablespoons (two 1/4-ounce packages) unflavored powdered gelatin
1/2 cup heavy cream
16 to 20 whole hazelnuts
1/2 cup heavy cream
4 ounces bittersweet chocolate (at least 60% cacao), broken into small pieces
1 tablespoon unsalted butter, softened
1 teaspoon hazelnut liqueur or amaretto (optional)
1 pint basket ripe strawberries
1 tablespoon plus 1 teaspoon sugar plus more if needed
1/2 cup heavy cream
4 glazed doughnuts without central holes or filling or other sweet bun such as brioche
1 large kiwi, peeled and very thinly sliced
12 fresh mint leaves (optional)
To make the gel&eacute;e: In a small, nonreactive saucepan, stir together the mango pur&eacute;e and sugar, adding the sugar by tablespoonfuls until the sweet-tart balance reaches your preference. Whisk in the gelatin until well mixed and set aside to soften for 2 minutes.
Prepare an ice-water bath by emptying a tray of ice cubes into a pan of cold water. Line a 12 by 9-inch baking pan or baking sheet with plastic wrap. Place the saucepan with the mango mixture over low heat, add the cream, and cook, while whisking gently to prevent sticking and scorching, until the mixture comes to a boil, about 4 minutes. Move the saucepan off the heat and into the ice-water bath. Whisk until the mixture has cooled to room temperature. Skim off any foam with a shallow spoon.
Pour the gel&eacute;e into the prepared pan. Refrigerate until set, about 1 hour. It keeps, covered and refrigerated, for 4 days.
To make the burgers: In a small, dry skillet, toast the nuts over medium heat, tossing frequently, until evenly light brown, about 5 minutes. Wrap the hot nuts in a clean kitchen towel and rub them against each other to rid them of their papery skins. Cut the nuts in half and reserve.
In a small saucepan over medium heat, bring the cream to a boil. Put the chocolate in a medium bowl and pour the hot cream over the chocolate. Cover, and let sit for 5 minutes. Then whisk until the chocolate is melted and smooth. Whisk in the butter and liqueur, if using. Let cool, stir in the hazelnuts, cover, and then refrigerate until stiff, about 1 hour.
Line a 3-inch round cookie cutter (or whatever size fits your bun) with a sheet of plastic wrap. Leave several inches of wrap hanging over the edge. Scoop one-quarter of the chocolate mixture into the mold. Use the wrap to smooth the ganache into a disc about 1/2 inch high. Gently lift out the burger in its wrap and refrigerate until needed. Repeat to shape the remaining 3 burgers.
Preheat the oven to 350?F. Choose 4 of the largest strawberries and cut them into very thin lengthwise slices. Pur&eacute;e the remaining berries in a food processor with about 1 tablespoon sugar (more or less to taste).
In a small bowl, beat the cream with the remaining 1 teaspoon sugar (more or less to taste) until it forms soft mounds. Cut the buns in half horizontally and place on a baking sheet, cut side down. Warm them in the oven for about 2 minutes. They should not be too hot or they will melt the chocolate burgers. Use the plastic wrap to transfer the mango gel&eacute;e onto a work surface. With a small, sharp knife, cut the gel&eacute;e into 3-inch squares, cutting through the plastic wrap as well.
To build the burgers, place each bun bottom on a dessert plate. Top each with a dollop of whipped cream, a circle of overlapping kiwi slices, and then berry slices, points outward. Add the chocolate burgers.
With the tip of a small knife, pry up a corner of each square of gel&eacute;e from its plastic wrap and peel it off. Arrange the gel&eacute;e on the burgers. Cover with the bun tops and tuck a few fresh mint leaves under the top buns, if using. If necessary, secure the top buns with toothpicks. Spoon a little strawberry sauce around the burgers and serve immediately.