Puffed-up miche - too much oven spring?
I made the mixed-flour miche from Hamelman today, and the oddest thing happened -- it puffed up like a football in the oven. It was very wide and flat (as usual) when I put it on the baking stone in a 450 degree oven (with steam). Eventually, it became oval, instead of the half-moon profile it usually has. Was this overproofed? Any ideas?