One of the most sought-after ingredients in Pokémon Café ReMix is hattrem, a rare ingredient that can only be obtained by completing certain tasks. To get hattrem, you'll need to first unlock the Addition Cooking feature at level 7 or higher. This allows you to combine two types of food to create new creations. Hattrem is only available at level 20 or higher in the game, though, so you'll need to use this feature quite a few times before you unlock it. Once you've unlocked the Addition Cooking feature, head over to your café kitchen and start mixing different foods to see what happens. Create as many new dishes as you can, and you may stumble upon the recipe for hattrem.