Desserts can be collected from defeated enemies, bosses, and destroyed objects. They are used to purchase permanent upgrades for Remi and to replenish Lore’s MP. All upgrades are retained even if you die or reset your story progress. When you die, you’ll lose a portion of the desserts you collected. You can mitigate this loss by purchasing the necessary upgrade.
So far, playing in Boss Rush mode is the fastest and easiest way to farm a lot of Desserts. Since the Boss Rush Mode can only be unlocked after completing story mode once, you can use the Suspend Game reload trick on boss levels to farm desserts and improve random weapon rotation early in the game. You can only carry a maximum of 999,999 dessert points.