Frozen White Chocolate Chunk Lime Mousse Meringata

For the Meringata:

Preheat oven to 225 degrees F. Position racks in the upper and lower thirds of the oven.

Line two baking sheets with parchment paper. It is helpful to double up your baking sheets if they are very thin—place the second sheet under the sheet lined with parchment paper.

In the bowl of a stand mixer using the whisk attachment, beat egg whites and cream of tartar on medium speed until foamy. Increase the speed to high and beat until soft peaks form. Add the sugar, about a tablespoon at a time, and beat for 5 seconds between additions. Add the vanilla extract and continue to beat on high speed until stiff peaks form and meringue is glossy. This will take about 4 minutes.

Transfer half of the meringue to a pastry bag fitted with a 1/2″ plain tip. Pipe the outline of a circle about 11″ wide on each cookie sheet—just eyeball it. Spoon the remaining meringue evenly into the center of each circle and spread to the edges making an even layer 1/2″ thick.

Bake the meringues for about 1 1/2 hours, until pale but very dry. They shouldn’t brown. Turn off the oven, prop the door open and let the meringues cool in the oven for several hours, until they are dry and crisp. If you are not filling the meringues right away you can go ahead and place each between pieces of parchment paper, wrap in plastic and freeze.

For the mousse:

Whisk together the lime zest, lime juice, eggs, sugar and salt in a small saucepan. Add the butter and whisk, cooking over medium-low heat, until it is thick enough to hold the marks of the whisk in the pan, about 5 minutes. Remove from heat.

Press the mixture through a fine mesh sieve into a small bowl to remove any lumps. Quick chill the bowl of mousse by placing the bowl in a larger bowl filled with ice. Stir occasionally until room temperature, about 5 minutes.

Whip the cream on medium speed until thickened. On low speed add 2 tablespoons powdered sugar and 1/4 teaspoon vanilla extract. Beat on high speed until stiff peaks form. Fold 1/2 of the cream into the lime mixture to lighten it, then fold in the remaining cream until just incorporated. Gently fold in the white chocolate chunks.

For the topping:

Combine blackberries, water and sugar in a small saucepan. Bring to a boil on high heat, stirring until sugar dissolves. Stir occasionally and continue to boil until sauce reduces slightly and thickens. Then remove from heat, cover the pan and refrigerate.

For the sugared blackberries:

Combine Just Whites and warm water in a small bowl, whisking for 2 minutes until whites are completely dissolved. Wash and dry the blackberries. Dip blackberries halfway into the egg white mixture, then into a small bowl of the granulated sugar. Lay them on a parchment lined baking sheet and allow to dry before using.

Assembly:

Place one meringue shell on a serving platter. Gently spread the lime mousse to within 1/2″ of the edge with a spatula. Top with the second meringue shell and press gently to adhere. Place in freezer for 15 minutes until slightly firm, then cover with plastic wrap and freeze 4-6 hours or up to 3 days ahead. Slice and serve as is or with blackberry sauce and sugared blackberries if desired.