After a meal of turkey sandwiches, crumpets, trifle, and Christmas cake, everyone felt too full and sleepy to do much before bed except sit and watch Percy chase Fred and George all over Gryffindor tower because they'd stolen his prefect badge.(PS12)
"You'll be singing a different tune soon enough, Hermione," said Fred, thickly buttering a crumpet. (OP12)
A sort of yeasty, rubbery bread formed into small, flat circlets and baked. The texture is not only rubbery, but full of holes. The finished product is meant to be grilled or griddled until slightly crunchy and served soaked in butter. Not the same thing as a muffin.