French Cuisine – How to Get Filling Inside Pâte à Choux?

This is because you are using a microwave. In theory, if you could turn off the microwaves in the microwave oven, you could use the convection function to bake things. In practice, we have had several questions which indicate that this is not how convection microwaves work. They keep nuking your dough, making it inedible. In your case, they are cooking all the moisture locally, resulting in mini-steam-explosions which create blisters, and a dried out, hard and crispy dough.

I am sorry, but there is no way you can bake with a microwave, not short pastry, and not other things. One exception might be quickly eaten "microwave cupcakes" which don't have much flour to start with and are baked for a very short time. I have seen people claim that they work, but never actually tried them.

For baking, you need a non-microwaving oven. The cheapest solution is a toaster oven with a 30x30 cm inner size, they are somewhat trickier to use than a big oven, but good enough for a small budget.

Technique for working with choux is important.

Sounds like you have the right oven temp to get that initial POOF! but sounds like the second stage is missing for working with larger shapes.

What we do in the bakery is start off at the high temp to get that steam expansion and slight crispness to the outside. We then turn the oven down about 50F-100F and continue to bake them so the dough cooks all the way through. At about the 3/4 point we'll sometimes quickly poke the bottoms to allow steam to escape easier.

Once you stuff the shells with your filling they get soft again so a really crispy shell isn't a big concern for us. It's about getting the right colour and the complete cooking in the middle. Also, if it doesn't quick work out you can do as another poster said, scoop out the under done dough.

Good luck!