troubleshooting hollow macarons

Whether using the Italian or French method for the meringue, I've never made a single macaron that's not hollow inside. Like these ones I baked recently, shown below. Although they may look almost perfect from the outside, I've always wanted to solve the issue.

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!