How to Make It
In a medium saucepan, combine the grape juice with the red wine, sugar and lemon juice and bring to a boil. Turn off the heat and let cool slightly. Add the pears and simmer over moderate heat until they are tender, about 20 minutes; let cool slightly. Using a slotted spoon, transfer the pears to a plate. Simmer the poaching liquid over moderate heat until thickened slightly, about 15 minutes.
Preheat the oven to 350° and line a large baking sheet with parchment paper. Spread the walnut halves on another baking sheet and toast them for about 9 minutes, until golden and fragrant. Let the walnuts cool completely. Coarsely chop the walnuts in a food processor. Add the 1 cup plus 2 1/2 tablespoons of confectioners' sugar and pulse until the walnuts are very finely ground, scraping down the sides of the bowl frequently. Transfer the walnut sugar to a bowl and whisk to break up any lumps. Increase the oven temperature to 425°.
In a medium bowl, beat the egg whites at medium speed until they are frothy. Increase the speed to high and beat until firm peaks form. Add the walnut sugar all at once and fold it in with a large rubber spatula until no streaks of white remain. (The meringue will deflate.)
Transfer the meringue to a large pastry bag fitted with a 1/2-inch plain round tip or to a sturdy plastic bag with a corner cut off. Pipe out 12 meringue mounds on the parchment-lined baking sheet, leaving at least 1 inch between them. Gently tap the baking sheet once on the work surface to smooth the tops. Sprinkle each macaroon with a tiny pinch of fleur de sel and bake for 4 minutes. Turn the oven down to 350° and prop the door open about 2 inches. Continue to bake the macaroons for about 12 minutes, or until the tops are brown and dry but the cookies are still soft. Let the macaroons cool for 5 minutes, then carefully transfer them to a wire rack to cool completely.
In a medium bowl, beat the clotted cream with the sugar until smooth and runny. Add the heavy cream and beat until soft peaks form.
To get 2 even slabs from each pear, first trim a thin slice from the bottom and trim off most of the top; cut the remainder in half horizontally. Using a small knife or melon baller, remove the cores. Place 6 of the macaroons, flat side up, on plates. Top each with a pair half and drizzle with some of the grape reduction. Spoon the cream on top and top with another macaroon. Dust with confectioners' sugar and serve.