Is it really that serious that a $2 tamale lives up to the hype though? I've been burned by too many "hidden gem" carts that just taste like regret and hot sauce.

Three years ago I did almost the exact same thing with a flourless chocolate torte that refused to set, and the cornstarch trick was a REAL lifesaver. I added a pinch of instant coffee along with the thickener and it took the edge off the sweetness, turned it into something my friends called "liquid brownie". The key for me was whisking like crazy while it was still warm, otherwise you get lumps that taste like raw paste. I also learned to keep a box of cornstarch near the stove now, it's saved me more times than I can count. Honestly, your version sounds better than the original cake, that sauce probably stayed moist way longer.