Answer :We posed this challenge to Patsy Jamieson, our recipe editor. Here are her thoughts: Certain recipes like basic muffin batters and quick breads are fine with canola oil, but many flaky pie crusts, cookies and cakes, in which the butter is creamed with sugar, do rely on a solid fat, such as butter, shortening or lard. In the case of pie pastry, the steam created between layers of solid fat and dough during baking is responsible for the flaky texture. Many cake recipes call for creaming butter and sugar until light and fluffy. Air is incorporated during this process, so it is critical to the leavening. I have never found a true substitute for butter in these types of recipes. I have had good results, however, replacing the butter with a 50/50 mixture of butter and canola oil.
I also lean towards the types of baking recipes that are easily adapted to using oil, rather than butter. For example, the oatmeal crisp recipe in the December issue is based on a classic wafer cookie, which uses melted butter and egg whites. It was easy to substitute canola oil for the melted butter. Cake batters that are lightened with beaten whole eggs (or a mixture of whole eggs and egg whites) are generally good candidates for swapping oil for butter. Light butters are not recommended for baking.