Bake the chocolate cake according to package instructions. Let it cool completely, then cut into small cubes.
In a saucepan, heat the raspberry liqueur, water, and raspberry jam over low heat until well combined. Let it cool.
In a mixing bowl, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
Melt the dark chocolate chips in a heatproof bowl over simmering water or in the microwave, stirring until smooth.
To assemble the trifle, layer the chocolate cake cubes, fresh raspberries, raspberry sauce, whipped cream, and melted chocolate in a trifle dish, repeating the layers until all ingredients are used.
Top the trifle with sliced almonds for added crunch and garnish with a few fresh raspberries.
Refrigerate the trifle for at least 2 hours before serving to allow the flavors to meld together.
Serve chilled and enjoy this decadent chocolate raspberry trifle!