Okashi na Tensei: Saikyou Pâtissier Isekai Kourin

A pastry chef with a promising future is reborn as the son of a poor lord. The boy's name is Pastry, and he will be the next lord of the territory. The struggles of young Pastry's story begin here as he aims to make people smile with his desserts and create a land flourishing with happiness. The best sweet comes with the best tale. This is a sweet fantasy that takes the royal road to change the world!

(Source: J-Novel Club)