In general, I find baking dairy-free reasonably easy - there are a lot of alternatives out there, and in general dairy-free baking doesn’t alter the recipe - be it Gluten-free or not. Eggs are another story, but we’re not going there today! I use Fleishmann’s Unsalted margarine (Kosher Pareve, no dairy, no casein) as a 1:1 substitute for butter when I bake. I use Soy Garden or Earth Balance tubs (both Vegan and Kosher Pareve, no dairy, no casein) margarine in place for butter in stove-top cooking. I use Spectrum Shortening for any shortening needs, but Crisco is also dairy-free.
I use rice milk, soy milk, water, or coconut milk (usually the latter) in place of any milk in baking. To make “sour cream” or “buttermilk” or even “yogurt” when its called for in recipes, I add 1TBS of lemon juice or vinegar per 1 cup “milk”, and it works just right in baking. Coconut milk works especially well for anything that needs more substance - ie: sour cream or yogurt substitutes. If you need “cream”, you can chill a coconut milk can, which separates it into a solid and a liquid. Scoop out (and heat) the solid, and you have the texture of cream, as well as the fat to carry flavor. Savory foods won’t taste coconutty, but sweet foods will have a bit of coconut taste, depending on the amount used (ie: if you use 1/4 cup coconut milk to 2 cups chocolate, no one will notice).
Once you are soy-free, things become more complicated. The liquid changes are the same, but the margarine changes aren’t. In some areas, Fleishmann’s sells a tub-product called “Fleishmann’s Light”, and it has no soy or dairy. The Fleishmann’s Unsalted that I currently use has soy oil, which is OK for some people who are avoiding soy, and not OK for others. If they aren’t available in your area, you can order them at Kosher.com.
For soy-free baking, I use Spectrum Shortening in place of butter/margarine. Spectrum Shortening can be found in most large grocery stores in the Health Food aisle, or in any health food store - including Gluten-Free Mall online. It worked well for me in baking and cooking, but it doesn’t have quite the same flavor, and is most definitely not a table spread. Flax oil worked as a “liquid butter” topping for my kids, but that might not work for everyone.
For a completely dairy-free and soy-free margarine, you want to start keeping your eyes out for Kosher grocery stores and even some Kosher delis. At Passover, they will sell Mother’s Margarine (Passover Version), which uses cottonseed oil as a base. It’s not an optimal oil in general, but it is allergy-safe. Many Kosher grocery stores keep the Kosher for Passover Mother’s Margarine in stock year-round. You can also order it online at various Kosher supply stores such as Kosher.com. As we get closer to Passover, it will be easier to find.
Chocolate is another one thats difficult if you’re soy-free. Most chocolate has soy lecithen, which is like soy oil - safe for some and unsafe for others. The EnjoyLife chocolate chips are soy-free, and most health food shops stock them - including Gluten-Free Mall online. This is another area where Kosher for Passover comes in handy - if you live in an area with Kosher grocery stores, you can get soy-free chocolate during the Passover season. Chocolate Emporium has lovely Dairy Free and Soy Free (and Gluten-free) treats near Passover - usually their treats have soy lecithen, but they are soy-free during Passover for religious reasons.
I need to edit some recipes to link back to this, and explain the substitutes that have worked for me over the years. We have now been at least somewhat dairy-free for 9 years, Gluten-free for 5 years, and during those 5 years we have been (at different times) soy-free, egg-free, corn-free, and now berry-free.
Do you have any dairy- and soy-free baking/cooking tips? What did I forget?