Why non-dairy buttercream curdles

In contrast to traditional dairy butter, the primary component of plant-based butter is oils like avocado, coconut, or a combination of various oils. As a result, you shouldn't expect it to perform exactly like dairy butter. One notable difference is that plant-based butter tends to have a higher moisture content, which can contribute to vegan buttercream being more prone to splitting. While vegan butter shares similarities with margarine in terms of ingredients, the crucial distinction is that margarine may contain milk solids, so they shouldn't be used interchangeably (though margarine is an excellent substitute for creating soft, fluffy baked goods).
Putting science and differences aside, the most effective way to achieve a smooth buttercream is to ensure that your main ingredient is at the ideal room temperature before mixing. Allow it to sit out for about an hour, depending on your kitchen's temperature. To further prevent curdling, make sure your milk is lukewarm, avoid adding excessive liquid, and mix just enough to combine the ingredients (but be careful not to overmix, as that can also lead to splitting).
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