Boil the sweet potatoes in the microwave and mash while its still hot. Add the margarine and sugar and mix. Add the egg yolk and mix well. Finally, add the heavy cream and mix together.

Put the pie sheets together (edges overlapping a bit) and use a rolling pin to roll it out to larger than the tart pan. Preheat the oven to 230℃.

Grease the tart pan with margarine and line with Step 2's pie sheet. Cut off the excess pie sheet, then use a fork to prick holes in the bottom of the pan.

Pour Step 1 into Step 3, then brush the entire surface with the ☆ egg yolk. Reduce the heat of the oven to 200℃ and bake on the lower rack for 10-15 minutes, upper rack for 20 minutes.

Remove from the oven, cover with a kitchen parchment sheet, and cool in the pan. Once cooled, remove from the pan and cut into pieces.

To easily remove from the pan, line the pan with parchment paper before baking so that you can neatly remove it.

If you mash the sweet potato to a slightly lumpy consistency, it has a beautiful texture, but it's also delicious if you use a food processor to make it smooth.

If it looks like it's going to burn, cover with aluminum foil and continue baking.

To make it crispy, heat the oven to a higher temperature at first so that it will become just the right temperature. (This is because when you open the oven to put the pan in, the temperature will drop.)

In this case, once you place the pan into the oven, set the temperature to 200℃ and bake.