Preheat oven to 350 degrees F.
You'll need a 10 inch tart pan with a removable bottom.
Grease and set aside.
In a large bowl or stand mixer, beat together the brown sugar, cream cheese and butter until light and creamy.
Mix in the egg, egg yolk and vanilla until thoroughly combined.
Stir the melted chocolate raspberry into the batter mixture.
In a separate bowl combine together the flour, cocoa powder, baking soda and salt.
On low speed mix the flour mixture into the batter mixture until combined.
Stir in the mini chocolate chips.
Scoop the batter into the prepared tart tin and smooth it out with an offset spatula until its evenly distributed.
Bake in the preheated oven for about 20 to 22 minutes or until a toothpick inserted in the middle comes out clean. Take care to not over bake as the tart can dry out.
In my oven, 20 minutes was sufficient and it had a soft yield to the touch. The tart will be puffed up slightly when ready and as its cooling it will deflate a little in the center.
Transfer the tart pan to a wire rack and allow to cool completely before piping on the buttercream.
In a small bowl beat ¼ cup of softened butter for 30 seconds on medium speed.
Add ½ cup of icing sugar, 1 tablespoon of seedless raspberry jam and 1½ teaspoon of milk and beat until combined.
Gradually beat in an additional ¾ cup of icing sugar.
Transfer the buttercream to a piping bag with the 1M tip attached and pipe the buttercream around the edges of the tart.
Dust with icing sugar then slice, serve and enjoy!