I am currently attempting a coffee-spice cupcake, and trying to alter a recipe I found online. Mostly I cook by intuition; I look at multiple recipes of the thing I'm trying to make, check ratios, and compile my own. You'd be surprised how hard it is to find a recipe for plain spice cake. You can buy it in a box, for sure, and there are recipes for molasses cake, but I've been having a devil of a time locating just plain ol' spice cake recipes. I finally found a few, but the one I ended up altering called for 4 teaspoons of baking powder. That seems like a lot to me.
Basically I'm working a cake recipe with ginger, cinnamon, allspice, nutmeg, clove, and instant coffee, and some molasses and two eggs in place of three eggs (one of the recipes had one cup of molasses and no eggs, and the other recipe called for three eggs, so I made a guess of it).
Currently I have a minute left on the timer, and it smells great, looks good....