Knead the butter into a paste. Add granulated sugar and mix until whitened.
Now add the egg yolks and the coffee creamer (add in small batches to ensure it doesn't separate).
Add the sifted flour into several batches. In cutting motion, fold in using a rubber spatula.
When smooth, press and knead with your hands. Bring the dough together.
Wrap in plastic wrap and chill for 30 minutes plus in the fridge.
Remove seeds from the kabocha squash and dice into 1 cm cubes. Cover with plastic wrap and steam in the microwave.
If using a microwave, 4 minutes at 700W. Or, use a steamer (don't simmer since it'll become watery). Set aside to cool.
Grease a tart pan with butter and coat with cake flour. Chill in the fridge.
Roll out the dough from Step 5. Press into the tart pan. Poke holes on the bottom with a fork.
Line with aluminum foil and put in the pie weights. Bake for 10 minutes at 170℃.
Set aside the baked crust to cool.
Combine the kabocha (Step 7) and all ingredients for the filling in a bowl and mix everything together. Pour into the baked tart crust. Bake for 20 minutes at 180℃. It's done when it's golden brown.
Story Behind this Recipe
I'm a member of a sweets seminar, and we agreed upon serving kabocha squash tarts at a school festival. So, I've finally managed to put this together after a few attempts. This is an improved recipe of this: [Recipe ID: 1059697]. You can also use readymade tart crusts. The filling is really easy to make, so please give it a try.
If the tart dough is turning runny, chill immediately in the fridge! Be extra careful during the summer. Don't forget to start with measuring the ingredients and preheating the oven.