I am experimenting with lightening a recipe and I've run into some trouble on my first try. The texture of the cake came out perfect, soft and moist, but the taste was a bit soapy. I would guess that this is a problem with leavening.
What I did was replace half of the butter with 1/4 the amount of yogurt and half the chocolate with dutch-processed cocoa (adding a little sugar and butter per ounce substituted for) and reduced the amount of sugar. The original recipe called for baking soda, and I did not change that (though I read that dutch-processed cocoa does not react well with baking soda) because I thought the acidity from the yogurt might be enough to counter the cocoa. I am no chemist, though, and I could really use help. Does anyone have an idea of where I might have went wrong?