Look for any Boston Cream Pie recipe. It's just a yellow cake with a pastry cream filling and a chocolate glaze on the top. Follow the directions for your pan and use the ingredients for the Boston Cream recipe.

More often than not, when you combine waxed paper with cake, especially a moist carrot cake, the paper tends to disintegrate, depending on how long it is in contact with the cake. Parchment paper tends to hold up a lot better, so you might want to try that. If parchment paper is not available, use what most cake decorators have relied upon for yearsPan Coating. I blogged about this years ago, and all it consists of is, equal parts shortening and flour (with a squirt, or two, of a neutral oil [e.g. Canola]) to make the mixture easier to brush onto the pan. The cake will not stick and you won't have to worry about serving bits of waxed paper with your cake :) Sol

My father's family had a chocolate version recipe and we called it "Dad's 3-Hole Cake"... always one of my favorites, especially when frosted with a cooked white frosting that isn't icky sweet, or just sprinkled w/ confectioner's sugar. The batter makes great cupcakes too. ETA: re the MW cake in a mug, I made up a gf recipe to try last year and it came out pretty good. I used a soup mug (wider and more shallow) rather than a coffee mug and I'd recommend that to help it cook more evenly in the MW.

I'm not so scientific. I think my 6” pans are 3”. Whatever they are, whether 6” or any other size, or deep mold like bundt, or loaf, I just make the batter, and fill to what looks right. If I have leftover batter, I just bake it off separately, either as a tester, or to use in something else. If I were baking commercially, I'd perfect the recipe amounts. As it is, I can't be bothered. I do have some anti-doming devices, but they don't work well enough, IMHO, to bother with most of the time. A cake fills best when perfectly flat, or even lightly dished. It's still going to need evening up. Many people prefer fewer taller layers (less “crust” to get rid of), and just slice them to the size they want. Others just make sheet cakes and cut their layers out of those. I just realized. My “eyeball” measure is about an inch from the top of the pan. That's what the half full and 2/3 full are both telling you. So the best way to get equal amounts of batter in each pan is to use a scale. For less formal, I just pour some batter in one pan and let it settle while pouring some in the other, then eyeball the height back and forth until the pans are filled properly. Usually once to start, a second time to divide the batter and a third to adjust and clean out the batter bowl. Measuring batter by volume is a good way to compare the recipe with the how much your pans will hold, but not an easy way to fill them. If you're worried your pans will overflow, you can line the sides with parchment paper or extenders made for the purpose. Don't fuss over precision unless there are judges involved. It's just cake. It's supposed to be fun. What's important is getting your batter in the pans promptly, a good whack to get out air pockets, and get them right in the oven. The moisture or acid acting part of the baking powder is already at work. If you leave the batter sitting around, it'll discharge and deflate. Some recipes do that on purpose for denser cakes, only lifted by the heat action and eggs, but if that's not your goal, make sure your oven has been at temperature for some time, so that the walls, not just the air, are hot, and you get your batter into the pans, and the pans into the oven promptly.