Hello everyone this is my first time asking a question so it is really important.  lol Every time I bake a white cake (from scratch) the taste is really good but I have been told that it is a bit dry.  I have tried different ways to mix the ingredients but nothing seems to work.  This is what I usually do:

Mix in 3/4 of a stick of butter with a cup of sugar for about 5 minutes until creamy.  Next I add in the dry mixture (3 cups of cake flour, 3 teaspoons of baking powder, and 1/2 teaspoon of salt) I add this in a little bit at a time alternating with 1 cup of milk.  I mix for about 2 minutes  until everything is incorporated.  Then I take my egg whites (4 egg white mixed with a hand mixer until soft peak, and add 1/2 cup of sugar gradually) I gently fold it into the mixture.  My chocolate cakes always come out perfect and moist but I have trouble with white cakes.  Also,I do put my cakes in the refrigerator in a box so it will be chill for transport.  What could I be doing wrong?  Any help would be greatly appreciated thanks!

You might be overbaking, sometimes the cake looks light and we think it needs to remain a little longer to brown. I was doing that with cupcakes but now it is only in 15-20 mins.

If your chocolate cake is coming out fine and IF you are using the exact same recipe are you replacing the cocoa quantity with extra flour?  If you are, try substituting cocoa with corn starch, that is what I do with my chiffon cake recipe. HTH.

AAt a glance, your recipe seems to lack liquid. Too much flour and not enough fat, or at least that's my gut reaction. I would expect to see a cup of sour cream in addition to the milk, or maybe just more milk. Also more butter.

But, I'm just a hobbyist, generally relying on the recipes and experience of others. Hopefully, others with more knowledge of baking chemistry will weigh in. For sake of comparison, consider this recipe for scratch white cake (I'm not sure where I picked it up):

5c cake flour 3 1/3c sugar 2Tb + 1tsp baking powder 2tsp salt 2 1/2c milk 1 1/3c shortening 16oz sour cream 1Tbsp vanilla 10 egg whites

That's a larger recipe than yours, but it has over twice as much butter/shortening and milk, plus sour cream, but not quite twice as much flour. Sylvia Weinstock's yellow cake is similarly more robust in terms of fat:

2 1/4c cake flour 2tsp baking powder 1/2 tsp salt 1/2 pound butter 2c sugar 4 large eggs yolks 2tsp vanilla 1c sour cream 4 large egg whites

Sylvia's cake has 3/4c less flour than yours, but over twice as much butter.

I hope that helps.

AHow much more butter should I add? Also I start out with 1 cup of milk but usually end up using a little more..so it's probably closer to 1 1/2 cup of milk. Thanks

If you like the recipe you are using and you only are finding it a tad dry misting your layers with a syrup solution. Just make a simple syrup out of sugar and water; put it in either a small spray bottle or whatever works best for you and just lightly apply to the torted layers before you put your butter-cream on.

i also keep my cakes in the fridge so i use only oil in those cakes, no butter -- because butter does not limber back up at room temp -- the cake will be as fresh as can be but the little bit firmer butter in there will drag down the back of the throat making it feel like it is dry -- it's the just the butter not loosened back up -- if you have uniced cake and you microwave it for 5 seconds it will be fully restored to it's lovely out of the oven lightness -- 

ergo i use doctored box mixes for white tier cakes so i can manipulate them in & out the fridge --

i use butter for cakes that we eat at home --

best to you