Preheat the oven to 350℉. Line a 9x9-inch baking pan with foil or parchment paper. Spray the foil/paper with nonstick spray and dust with flour. Or spray with baking spray.
PREPARE THE CAKE:
In a medium saucepan, stir the chocolate and butter over low heat until melted and smooth. Add the jam and whisk until melted. Remove from heat and cool slightly.
In a large bowl, use an electric mixer to beat the sugar and eggs until the mixture thickens, about 5 minutes. Sift the flour and baking powder over the egg mixture and fold it in with a rubber spatula. Gradually fold in the chocolate mixture too.
Pour the batter into the prepared pan. Bake until the top of the cake is slightly crusty, begins to crack and tester inserted into center comes out with moist crumbs attached, about 45 minutes. Cool 5 minutes. Gently press down any raised edges of cake to even. Let cool in the pan. When completely cooled, turn the cake onto a platter. Peel off the foil. Trim ½-inch off each edge of the cake to make it nice and even and pretty-looking.
PREPARE THE GLAZE:
Stir the cream and jam in a heavy small saucepan over medium heat until the jam melts; bring to a boil. Remove from heat. Add the chocolate and stir until melted. Let stand until cool but still spreadable, about 15 minutes.
Spread the glaze over the top of the cake. Immediately arrange the berries on top of the glaze. Chill about 10 minutes, or until the glaze sets.
Cut into 12 bars and serve.
Notes
*These bars may be prepared one day ahead. Keep chilled.