Chocolate Truffle Tarts

Name: Chocolate Truffle Tarts
Ingredients: 1 stick (113gr) unsalted butter, at room temperature; 1/2 cup (60gr) unsifted powdered sugar; 3 egg yolks; pinch of salt; 1 cup (160gr) white rice flour; 1/4 cup (30gr) amaranth flour (you could use sorghum flour); 1/4 (40gr) potato starch; 1/4 cup (20gr) unsweetened cocoa powder; 8 ounces (240gr) bittersweet chocolate; 12 tablespoons (170gr) unsalted butter, at room temperature; 1/4 (50gr) cup sugar; 1/4 cup (60ml) strong brewed coffee; 4 large eggs; 4 ounces (120gr) bittersweet chocolate; 1/3 cup heavy whipping cream; 2 tablespoons unsalted butter, at room temperature