How to Make It
Prepare the crust: Preheat oven to 350°F. Grease and flour 2 (12-cup) mini muffin pans. Process 1 1/4 cups nut mix in a food processor until very finely chopped, about 30 seconds. Place finely chopped nuts in a medium bowl; add salt. Place egg white in a medium bowl; beat with an electric mixer on high speed until stiff peaks form, 1 to 2 minutes. Fold beaten egg white into finely chopped nut mixture. (Mixture will be sticky.) Spoon about 1 teaspoon nut mixture into each cup of prepared muffin pans. With floured fingers, press nut mixture in bottom and up sides of muffin cups to form a crust. Bake at 350°F until beginning to brown around the edges, about 5 minutes. (Egg white will bubble up while baking.) Remove from oven, and let cool in pans to room temperature.
Prepare the filling: Pulse remaining 1 1/4 cups nut mix in food processor until coarsely chopped, about 7 times. Transfer coarsely chopped nuts to a medium bowl; add miniature chocolate chips. Spoon about 1 tablespoon nut mixture into each muffin cup. Heat brown sugar, granulated sugar, and date syrup in a small saucepan over medium until sugars are completely dissolved, about 5 minutes. Remove from heat. Stir in half-and-half, butter, and vanilla. Let cool to room temperature, about 20 minutes. Lightly beat eggs with a fork. Add eggs to cooled sugar mixture, whisking well to combine. Pour about 1 tablespoon sugar mixture over each filled cup. Bake on bottom rack of oven at 350°F until just set, 12 to 14 minutes. Let cool in muffin pans 10 minutes. Run a knife around edges of each pie, and remove pies to wire racks to cool completely, about 20 minutes. Place bittersweet chocolate in a microwavable bowl. Microwave at high until melted, about 1 minute, stopping to stir halfway through. Drizzle chocolate over pies. Refrigerate at least 30 minutes. Serve chilled or at room temperature.