Cognac is like the glencairn bulb on steroids. Those are pretty wide glasses, and they have a longer stem so you can use your palm to heat up the brandy.

https://www.amazon.com/dp/B07K1NHC5T/ref=cm_sw_r_sms_awdb_t1_QgDvEbP99METJ

I usually go glencairn, but I’ll admit, an old fashioned crystal glass looks a lot cooler.