To make a prismatic donut in the game Grow a Garden (Grow a Garden Cooking Event on Roblox), there are several recipes using different combinations of special crops. The most common and recommended recipes for a prismatic donut involve the ingredients bone blossom and sugarglaze, which are prismatic crops needed for the highest rarity donut. Here are some prismatic donut recipes:

• 1 Sugarglaze + 4 Bone Blossoms
• 2 Bone Blossoms + 1 Sugarglaze
• 3 Bone Blossoms + 1 Ember Lily + 1 Sugarglaze
• 3 Bone Blossoms + 1 Sugar Apple + 1 Banana
• 4 Bone Blossoms + 1 Banana
• 2 Bone Blossoms + 2 Elder Strawberry + 1 Sugarglaze

Bone Blossom is a rare crop mostly obtained via trading, and Sugarglaze comes from the Gourmet Seed Pack reward. Using larger crops in cooking increases the rewards. So, the basic step to make a prismatic donut is to use the cooking pot in the event hub, combine bone blossom(s) with sugarglaze, optionally with other special crops like ember lily, sugar apple, banana, or elder strawberry depending on the recipe chosen, then cook the mixture.

This is specifically for the context of the Grow a Garden game; if the "prismatic donut" means something else (like a real-world recipe or different game), please clarify.