Frosting with Malt not GF what can we use?

If you live near a Japanese or Korean market, or have time to order online, try kinako (bokkeun konggaru). It's flour made from full-fat roasted soybeans that supposedly has a sweet, nutty flavor. Stella Parks of Serious Eats and BraveTart uses it as a replacement for malted milk powder, though I don't think it's a 1:1 substitution and she doesn't give an exact ratio - in one recipe she calls for 2/3c kinako in place of 1/2c malted milk powder, but it's part of an overall gluten free flour blend. You might have to tinker with it.

That's a good question. Malts are most often made with barley and wheat- which of course are not gluten free. There are other grains which are malted- particularly sorghum, but those generally come in syrup or dried grain form and meant for brewing. You could use that for cooking and sweetening purposes, but not in this recipe as it is written, I think. If you can find sorghum syrup, you can use that to make a frosting in place of corn syrup- and I think you could easily use the malted syrup in the same way. It would not be this specific frosting- but it would be gluten free, and have some of the malt flavor.