The only time I've seen butter flavouring in a recipe is for 'buttercream' icing made with shortening (Trex), to achieve a bright white icing. This type of 'buttercream' tastes nowhere near as good as one made with butter, so clear butter flavour can be added for flavour. Wilton make clear/colourless butter flavour, I've tried to buy some but always unsuccessfully. I'm sure, even with the butter flavour, the shortening buttercream will still taste very inferior to the real stuff. But I still want to try.