Can you smear butter on your challah? Can you make a dairy challah with cheese inside? Both are doable, but with certain caveats.
There are various halachos regarding the baking of bread and challah, and one of those is that bread should always be pareve. However, there are a few exceptions to the rule.
- Cheese may be put on top of the challah, if clearly visible.
- When making dairy challah one should only bake enough for one meal.
- If you want to add dairy ingredients (milk, butter, cheese) in the actual dough it must be shaped differently from typical bread or challah.
So recipes like this Spinach and Feta Stuffed Challah may be problematic, unless you make sure the cheese can be seen on top.
If you want to spread butter on your challah, obviously you need pareve challah, i.e. challah not baked in a meat oven. Also, you cannot put butter on leftovers of challah that were sitting on the table during a meat meal.