Any glass bowl, cup, etc. should be 'microwavable,' assuming it doesn't have any metallic decorations on it. Even a plastic container will work as long as you don't try boiling stuff in it. Of course, the plastic type may be made of low temp stuff and melt before you want it to! And it can also 'outgas' rather toxic chemicals. But, you mighty actually enjoy the 'extra' 'flavors!'
The first (OK, two) criteria for be 'microwavable' is no metal and non-liquid absorbing material. For example, kiln dried pottery is usually OK, if you're sure there are no spots that might allow water into the clay. Water is one of the most reactive chemicals to microwaves. And it's obviously one of the most used in chemical in cooking, so anything that might trap water in it could easily break if heated too long, often before the item being heated reaches the stage you want. And the 'breaking' may be more like an explosion!
My real question is: will this recipe work in my Betty Crocker/Play School stove's oven?
I think I will simply maintain my status as the Official, Self-appointed, TS Dessert Taster. Please PM for my mailing address and pack items well and insulated, if needed. Thanks!