(adapted from Tartine)
For the crust:
½ cup (2 ounces) confectioners’ sugar
1½ cups (7.5 ounces) all-purpose flour
6 ounces salted margarine*, (I like earth balance whipped buttery spread)
For the filling:
2¼ cups (16 ounces) sugar
2 cups (20 grams or .75 oz) loosely packed fresh spearmint leaves
½ cup (2½ ounces) all-purpose flour
1 cup plus 2 tablespoons lemon juice
Finely grated zest from 2 lemons
6 large whole eggs
2 large egg yolk
confectioners’ sugar for topping (optional)
*If using unsalted margarine add a pinch of salt to the filling.
Preheat the oven to 350 degrees and butter a 9-by-13-inch baking pan.
To make the crust: Sift the confectioners’ sugar into the bowl of a stand mixer fitted with the paddle attachment. Stir in the flour. Add the margarine and beat on low speed just until a smooth dough forms.
Press the dough evenly into the pan and allow it to come up about a ½ inch up the sides of the pan. Line the crust with parchment paper or foil and fill with pie weights. Bake the crust until it is a deep golden brown, about 25-35 minutes.
While the crust is baking make the filling. Place the sugar and mint in the bowl of a food processor and process until finely ground. Add the flour and pulse until combined. Place the flour/sugar mixture in a large bowl and add the lemon juice and zest. Stir to dissolve the sugar. In a separate mixing bowl, whisk the whole eggs and egg yolks (and the salt if using). Add the eggs to the lemon juice mixture and whisk until well mixed.
Once the crust is ready, pour the filling directly into the pan. Reduce the oven temperature to 300 degrees and bake just until the center of the custard is set, about 30 to 40 minutes.
Let cool completely on a wire rock, then cover and chill well before cutting. Cut into squares and dust the top with confectioners’ sugar, if desired. They will keep in an airtight container or well covered in the baking dish in the refrigerator for up to 4 days.