6 oz (170 g) bittersweet chocolate, chopped
1 cup (250 mL) butter, softened
1/4 cup (60 mL) granulated sugar
1-1/2 tsp (7 mL) vanilla
2-1/4 cups (550 mL) all-purpose flour
1/4 cup (60 mL) cornstarch
1 tsp (5 mL) cinnamon
1/2 tsp (2 mL) pepper
1/2 tsp (2 mL) ancho chili pepper
1/4 tsp (1 mL) salt
2 oz (57 g) bittersweet chocolate, melted
In heatproof bowl over saucepan of hot (not boiling) water, melt chocolate, stirring occasionally. Remove from heat; let cool.
In bowl, beat butter until fluffy; beat in chocolate until smooth. Beat in sugar and vanilla. In separate bowl, whisk together flour, cornstarch, cinnamon, pepper, ancho chili pepper and salt ; stir into chocolate mixture.
On parchment paper, shape half of the dough into 10-inch (25 cm) log. Repeat for second log. Wrap and flatten to create triangular logs. Refrigerate until firm, about 2 hours, reshaping logs if necessary. (Make-ahead: Freeze in airtight container up to 3 weeks.)
Cut logs into generous 1/4-inch (5 mm) thick slices. Arrange, 1 inch (2.5 cm) apart, on parchment paper–lined baking sheets. (If dough softens, freeze for 15 minutes.)
Bake in 325°F (160°C) oven until firm, about 20 minutes. Let cool on pans on racks for 2 minutes. Transfer to racks; let cool completely.
Topping: Using piping bag or fork, drizzle cookies with chocolate; refrigerate until set, about 30 minutes.