1. Heat oven to 375 degrees F. In large bowl, combine piecrust mix, sugar and cocoa powder until well blended. With whisk or fork, gradually stir in just enough water until dough starts to stick together. With hands, gather dough into a ball.
2. Cut off 1/3 of dough. On lightly floured pastry cloth or surface, roll into a 12 x 6-inch rectangle. Place on waxed-paper-lined baking sheet; refrigerate. On lightly floured surface, roll remaining 2/3 dough into 10-inch square. Fit into 9-inch-square tart pan with removable bottom, trimming dough from edge. Prick bottom with fork. Line crust with sheet of foil; fill with pie weights or dried beans.
3. Bake at 375 degrees F for 10 minutes. Remove foil and beans; return to oven. Bake 10 minutes longer.
4. Meanwhile, in small saucepan, over medium-high heat, heat cream just until bubbles form around edge. Remove from heat; stir in chocolate. Let stand 1 minute. Whisk until smooth. Let chocolate mixture cool slightly. Whisk in eggs.
5. Remove crust from oven; immediately spoon raspberry jam over bottom of crust. Spread evenly as jam melts. Pour chocolate mixture evenly over jam.
6. Cut pastry rectangle into eight 12 x 3/4-inch strips. Cut two strips crosswise in half; use these for the corners. Place pastry strips on top of chocolate filling in a lattice pattern, trimming edges.
7. Bake at 375 degrees F for 25 minutes. Let cool completely. Remove side of tart pan. Can be served at room temperature or cold.