Easy Potato Gratin but not light

Overview

“I knew I should have waited until spring." Natsuki was depressed as soon as she got home. She pretended not to notice the disturbing skies and put on the leather shoes she had fallen in love with at first sight, but as expected, it rained. After wiping off the water and praying that it would not stain my shoes, I realized that I was also wet and cold. "On a day like this, I needed something hot to eat." Wearing a colorful apron, Natsuki heads for the kitchen. Today's dish is ...... gratin.