How to bake the Betty Crocker Super Moist White Cake

If you try to break this all up, it's possible that people will try to shut them down as being duplicates. (and they close to a few others, but I don't think they're true duplicates)

1. I don't know if a 1.5" high pan would be tall enough. I've done what you're asking about, but in a 3" high 8" across pan, and it comes up to the top (at least, the dome does). As an 8" is about 80% of the area of a 9", so I'd expect it to rise to about 2.4". See How much can I change the height of a cake? and Correct way to join two halves of sponge cake?

2. Don't increase the number of egg whites. You're already adding more water by changing the oil to butter. (as butter is about 15% water). Keep the egg whites the same. See Conversion rule: how to switch oil and butter? and for the inverse, Can vegetable oil be used in place of butter? (which links to lots of others).

3. You can only get away with it if you're baking them all at the same time, as letting it sit before baking will change the texture. Of course, that would require having multiple pans, and enough space in your oven to fit them all in without crowding. (and related : Cakes cooked in same tin but come out different sizes )

   But if you're going to be making 4 times the batter, I'd actually recommend making 3 cakes rather than cramming it all into two. (although, I'd feel better if your pans were 2" high.

4. Yes, lower the heat to reduce doming. (also see How do you make a cake lift equally and minimize doming? ). And you cook them until they're done. (I will never bake a 14" cake again if I can help it, as even with baking strips and a heat core, the outside was done so much sooner than the inside that I had to turn the oven down so far that it took hours to finish).

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Oh, and 'super moist' cakes aren't so great for stacking really high. You typically want a denser cake (eg, pound cake), so the weight of the upper layers don't crush the bottom. As they end to be dryer, you then pour on some flavored syrup to soak in.

There is a trick for dealing with boxed mixes though -- add a package (one of the smaller boxes) of instant pudding in with the cake mix, without adding any of the stuff that the instant pudding calls for adding. But it'll change the color of your cake, if you were hoping for snow white.

Four thick layers is a very tall cake! The affects not only the proportion of the size of the cake, but also the size of the slices. Do you want slices that are 6-8 inches side to side?

Why not make three mixes and divide them among four pans. That might work out okay.

When you are thinking of modifying a recipe, it's a good idea to do the basic recipe first so you know what you're dealing with.

As to heating cores -- you shouldn't need them for a cake less than 10 inches. For large cakes, I put in several heating cores.

Heating strips are very helpful, but why the aluminum foil? I just tied wet towel strips around the pan until I got my Wilton strips.

If you don't want "dome" on your cake you can always level it off using a knife or a "cake leveler" ("tortenschneider" in German!) to take off the dome.

If you want a butter cake why don't you get a scratch recipe and make that? Butter and oil cakes are often mixed differently. A white oil cake may have a better color than one made with butter (which, after all, is yellow.) To get butter flavor you can find colorless butter flavoring for baking (Wilton, maybe?) There is also colorless vanilla. These are useful for white cakes (I speculate they exist to help people who want a really white wedding cake.)

Finally -- best of luck to you. Don't be "afraid" of what will happen; think of yourself as curious about what will happen. We call it "gaining experience."

You asked many questions, here is a partial answer to the fourth one - how to use baking strips best against doming.

I have trouble getting my Wilton Fabric Strips to stay on a rectangular cake pan. My solution was to buy two aluminum, disposable cake pans. Cake batter goes into one pan. The second pan I line with my wet fabric strips, and place the batter filled pan, into the lined pan. So my fabric strips are sandwiched in between the two aluminum pans. I then bake at 325 degrees, and add ten more minutes to the baking time