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Boxed cake mix often calls for minimum or low grade ingredients. Thus, one of the east ways to improve your cake mix is by substituting certain ingredients for others. The box cake will wind up tasting richer and homemade.  Substitute milk for water. Switch out low fat milk for cream or whole milk Use coffee instead of water in chocolate cakes. This will add a richer and more complex flavor to your cake. Perhaps the easiest way to improve your boxed cake mix is to add more called-for ingredients. By adding ingredients, you’ll make the cake richer and have better flavor. In the end, your cake will seem more like a homemade cake than a store-bought box cake.  Add more eggs. For instance, if the box calls for two eggs, add a third. This will make the cake taste richer. Increase the amount of sugar. Do this carefully, though. Consider adding maybe 10% or 20% more than the box calls for. Pour in more vanilla. More vanilla may add more flavor and enrich your boxed cake. Like with sugar, only add 10% or 20% more. By expanding the recipe, you’ll not only enlarge your end product, but create the opportunity to use new and better ingredients. In the end, you’ll have more cake to share with your family.  Double the ingredients. For instance, if it calls for two eggs, use four. You may need to add extra ingredients like flour, sugar, baking powder, and more. Make sure you adjust all your ingredients proportionately. For example, don’t add more flour unless you add more sugar, eggs, milk, and everything else.
Substitute ingredients. Add more ingredients. Expand the recipe.