I went to primary school mid 90s and we used to have this dessert as part of our school lunch.
It was chocolate orange themed I'd say. Cut into squares from like a tray bake type thing. It was served cold. Had a chocolate crispy base, not sure if it was maybe Cornflakes or something similar coated in chocolate. It was sort of constructed like cheesecake, except the cheesecake layer was quite jelly like and orange Flavoured but not clear like jelly and a bit creamier.
This has literally bugged me for years because it was my favourite at school and I've never seen anything like it since and have no idea what it's called or if we had a michelin starred lunch lady 😅