After my macaron troubleshooting project recently using different recipes and oven temperatures, I finally found the answer. The single baking sheet I was using all the time wasn't insulated enough and the macarons were rising too fast creating taller feet and hollow interiors.
The solution: I just put one baking sheet on top of another and proceeded to line it with parchment paper. A cross section of the ube macaron is shown below. They're very delicate and finicky but I think I found the right combination of mixing technique and oven temperature that worked for me. The extra insulation underneath was crucial when baking them with parchment paper. I think with Silpat (a reusable nonstick liner) a single baking sheet will be fine. Silpat is much thicker than parchment paper and provides much better insulation.
|finally...macarons that are not hollow inside!|