Popovers. Little help please?

Before the collapse

The other night, I was able to get home a bit early and make some beer-braised short ribs and noodles for dinner. Totally psyched, but I made a mistake and didn't make enough noodles and wanted to add a bit more starch to the meal. Popovers. Perfect. Could any bread be more straightforward?

milk, salt, egg, flour, mix, rest, drop into buttered, preheated muffin tin, poof, voilà. After baking 450°F for 5 min and 400°F for 20 min they looked wonderful. I took them out of the oven, a quick photo, turned my head, flop. Within a few seconds they were limp blobs of dough, not the huge, crisp popovers they were a minute before. This is the second time it has happened to me.

Update
Rachel commented that maybe I should've cooked 'em longer. The recipe I followed was from Ruhlman's Ratio. In Ratio, the cooking temp/time sequence is 450F/10 minutes, followed by 375F/20-30 min. In Ruhlman's blogpost, the baking instructions are "450 till done."

Mrs. Dave's Beer, an accomplished but oft-bullied-out-of-the-kitchen baker herself recommended the Better Homes and Gardens recipe. "It has never failed" she declared (she's right, she makes killer popovers). The recipe from BH&G is nearly identical with the exception that the muffin pan is lubed with shortening and there's a tablespoon of oil per 200 g of dough and the baking instructions are significantly different. BH&G prescribes 450F/20 minutes followed by 350F for 15 to 20 min or till very firm." The BH&G recipe continues to say (I'm sorry for violating all kinds of legal stuff, but this is important)

"If popovers brown too quickly, turn off oven and finish baking in the cooling oven till very firm. A few minutes before removing from oven, prick each popover with a fork to let steam escape."

With that much commentary after the baking temperature and time, I gather the recipe has produced a sunken popover or two prior to publication.

My take on this? The initial high temperature is needed for the oven spring and then the rest of the baking is for stengthening the exterior, yet not burning the outside. So, I'm with the more careful version of baking provided by BH&G. Don't know if the pricking with a fork is necessary, but I'll do it. Let you know how it goes.