In his manuscript notebook Thoreau also describes walnuts ripening in the fall: “high-scented, aromatic,” he wrote, “almost like nutmegs, only more bracing and northern.” Their texture and flavor complement Concord grapes well, so they are included here without spices.
1 (single) 9-inch walnut tart shell:
¼ cup walnuts (unsalted), lightly toasted
2 tablespoons sugar
1 cup flour
6 tablespoons unsalted butter (¾ stick), very cold, cut in
Pinch of salt
1 large egg
Concord grape filling:
1½ pounds (about 4 cups) Concord grapes, stemmed
4 tablespoons cornstarch
2 tablespoons fresh lemon juice
½ cup sugar, or to taste
1 tablespoon grated lemon zest
½ cup sugar
½ cup flour
6 tablespoons (¾ stick) unsalted butter, softened, cut in small pieces ⅔ cup chopped walnuts (unsalted), lightly toasted
First make your tart shell. Put the walnuts and sugar in the bowl of a food processor and coarsely chop the nuts for a few seconds (the sugar will keep the nuts from turning oily). Add the flour, butter and salt, and process until the butter is cut into bits. Then add the egg and process just until a ball clumps on the blades, no longer. Wrap the ball in plastic and chill for at least an hour, overnight if you like.
Roll the dough out on a lightly floured board and fit it into a 9-inch pie or tart pan (use a sturdy one). This dough is rich and crumbly, so be patient. Trim and flute the edges; prick the inside of the shell with the tines of a fork. Cover with plastic wrap and chill well.
Meanwhile, make the grape filling. Slip the Concord grape pulp from the skins into a pot, saving the skins. Cook the pulp over low heat for a few minutes until it softens, then press the pulp through a sieve with the back of a spoon to separate the seeds. Add the pulp to the skins in the pot and discard the seeds. You will have about 3½ cups. When you are ready to bake the tart, preheat the oven to 450°. Place the tart shell on a baking sheet and prick it with the tines of a fork. Bake it on the middle rack of the preheated oven for 10 minutes.
While it is baking, mix the cornstarch with the lemon juice into a smooth paste. Stir this with the zest and sugar into the grape pulp.
For the streusel, combine the sugar and flour in a mediumsize bowl. Add the butter pieces, and with your fingertips work the butter in to make crumbles. Mix in the walnuts. Take the tart shell out of the oven (if it has puffed up, prick or press to deflate it). Fill it with the grape mixture; do not overfill. Scatter the streusel over the surface. With steady hands, carefully put the tart back in the oven. Bake for 10 minutes, then lower the heat to 350° and bake about 30 minutes longer, when the filling should be set and the topping golden brown. Cool the tart on a rack, cut it into wedges and serve if you like with vanilla ice cream.
Makes eight servings.
Special thanks to Jay Hardenburg of The National Grape Cooperative Association, Welch’s and to John Baccoli of AgriAmerica, LLC, for finding Concord grapes for me.