Preheat oven to 350°F (180° C) and line mini-muffin tins with cupcake liners. Spray liners with cooking spray.
Melt butter and chocolate in a 4-quart heavy pot over moderately low heat, stirring until smooth. Whisk together flour, cocoa, and salt. Remove pan from heat and whisk in granulated sugar. Add eggs, 1 at a time, whisking after each addition until incorporated, and stir in flour mixture just until blended.
Spoon batter into muffin liners, filling cups to top, and bake in middle of oven 25 to 30 minutes, or until a tester comes out with crumbs adhering. Cool 5 minutes in tins and turn out onto racks. Repeat with remaining batter.
Dust with confectioners' sugar if desired.
Cupcakes may be made 2 days ahead and kept in an airtight container at room temperature.
Makes about 72 mini-cupcakes.
Source: Gourmet Magazine-December 1999
Date: Februaruy 21, 2003