For the batter: Bring butter to room temperature and cream until soft. Add powdered sugar and beat until white and fluffy.
Add a beaten egg (also brought to room temperature) little by little and mix well. Add the sifted flour and stir until combined. Wrap the batter in plastic wrap and chill in the fridge.
Make the filling while the batter is chilling. Remove the seeds from the kabocha squash and rinse well. Wrap the squash in plastic wrap and microwave until soft (About 3 minutes in my microwave, but adjust the time depending on the kabocha).
Spoon out the inside of the squash into a bowl, being careful not to tear the rind, since you will use it to decorate.
Mash the squash while hot (a wooden pestle works well). Add sugar and mix well. When it has slightly cooled, add the eggs, heavy cream, raisins and stir well. Finally, add the rum or rum essence and mix well.
Cut out the rind into any shape you like.
Line a tart pan with pie crust and prick the surface with a fork. Pour in the chilled batter and arrange the decorations on top. Bake in a preheated oven at 320/160C for 25-30 minutes.
Brush the baked tart with mango jam, let cool and it's ready to eat.
Story Behind this Recipe
I made it to take to a Halloween party for grown-ups.
There is no need to strain the squash. I used a wooden pestle, which worked fine. If you want to taste bits of kabocha in the filing, it would be good to use a fork or masher instead to keep some lumpy consistency. I used mango jam because I thought it wouldn't overpower the sweetness of the squash. The glaze is optional.