For the truffle filling:
1/2 cup heavy cream
2 tablespoons brown-rice syrup
8 ounces high-quality bittersweet chocolate, finely chopped
1 tablespoon cognac
Pistachio cookie base:
1 cup plus 3 tablespoons shelled pistachios, divided
1/4 cup granulated sugar
1 tablespoon cornstarch
1/4 teaspoon fine sea salt
1 large egg white
1 teaspoons vanilla extract
1/8 teaspoon almond extract
For the chocolate shell:
6 ounces high-quality bittersweet chocolate, roughly chopped
1 tablespoon extra-virgin coconut oil
Make the truffle filling:
In a small saucepan, heat cream and brown rice syrup over medium heat until it just begins to simmer. Immediately remove the pot from heat and add chocolate. Let stand for 3 minutes, then stir until chocolate is melted and smooth. Add cognac and stir to combine.
Transfer truffle filling to a medium bowl and let stand at room temperature until the texture thickens and resembles peanut butter, whisking occasionally, about 45 minutes.
Make the cookies:
Arrange the racks in the upper and lower rungs in the oven and preheat the oven to 325°F. In the bowl of a food processor, pulse 3 tablespoons pistachios until very finely ground and powdery. Set ground pistachios aside.
In the bowl of a food processor, combine remaining 1 cup pistachios, sugar, cornstarch, and salt; pulse until very finely ground. Add the egg white, vanilla extract, and almond extract, and pulse until well combined.
Drop dough by teaspoonfuls onto two parchment-lined baking sheets, spacing them 1 inch apart. Use a finger dipped in water to gently flatten the pistachio rounds until they are about 1 inch in diameter. Bake until the cookies are set and edges are golden, about 12 minutes. Let the cookies to cool completely, then freeze cookies for 1 hour.
Assemble the cookies:
Once the cookies have been frozen, spoon 1/2 teaspoon truffle filling on the flat side of each cookie. Use a butter knife or small offset spatula to shape the filling to a domed point. Freeze cookies until the filling is set, about 15 minutes more. Place cookies on a wire rack placed over a parchment-lined rimmed baking sheet.
In a heatproof bowl set over a medium saucepan of barely simmering water, combine the 6 ounces of chocolate and the coconut oil. Stir until mixture is smooth; remove from heat and let cool slightly.
Finish the cookies:
Working with one cookie at a time, spoon the chocolate shell over the cookies to completely enclose the filling. Sprinkle the top of each cookie with a pinch of reserve ground pistachio while the glaze is still wet. Let cool completely before serving.