1. Mix flour, cocoa, baking powder, and espresso powder; set aside.
2. In a large bowl, beat 1/2 cup butter and granulated sugar with a mixer on high speed until fluffy. Add eggs and vanilla; beat until blended. Add flour mixture, about a third at a time, mixing on low speed until blended.
3. Stir in chocolate chips, nuts, and raisins.
4. Lightly butter a 9-inch tart pan with removable rim. Spread batter in pan.
5. Bake in a 325° oven just until cake begins to pull away from rim, 25 to 30 minutes. Set on rack to cool. To serve, warm or cool, remove pan rim, lightly dust torte with powdered sugar, and cut into wedges.