Yorky, do you have a recipe for this?
(I'll check on the desktop later).
Something I've discovered about halogen oven cooking. I broke the lid to my larger Pyrex casserole dish some time ago and haven't got around to replacing it. I needed the larger one for the potato au gratin so I used aluminium foil as a make shift lid. After 1 hour (checked at 15 minute intervals) the potatoes were hardly cooked. I'm presuming that the foil interferes with the halogen "waves"?
I don't think so. The Halogen is simply a heat source. I use foil sometimes if the top of something looks like its browning too quickly. Maybe its because the original lid is a tight seal? I could be wrong - I don't usually use foil in the halogen so I'm only basing it on my limited experience.