Peel the kabocha squash and cut into 5 mm pieces. Rinse lightly and put into a heatproof bowl. Cover loosely with plastic wrap and microwave at 500 W for 4-5 minutes.

After the kabocha is soft, mash with a masher or a fork. If you mash it roughly and leave it a little chunky, the cookies will be really tasty. Start preheating the oven now!

Put the butter (brought to room temperature) in a bowl and add the sugar in 2 batches, stirring well to blend after each addition.

Add the beaten egg and mix quickly to prevent separation.

Add the cooled mashed kabocha squash. Mix again.

Sift the cake flour 3 times. Add the cake flour and the sesame seeds and fold into the dough with a rubber spatula.

Just before the dough is completely combined, mix in a few drops of vanilla oil. The dough is ready.

The finished dough will look like this.

Using 2 spoons, drop the cookies onto a baking sheet. If they're too big, they might not cook through, so make them about 25 mm in diameter.

Bake in an oven preheated to 340F/170C for 15-18 minutes. When the cookies are golden brown, they're done! The outside will be crispy and the inside will be soft. Delicious!