Not high, but high enough to bring it to a boil.
It's something you come to understand very fast when it starts to warm up, lol.
Too hot, it'll boil itself out of the pot;
Too low, wont boil;
There's a sweet spot depending on how much honey you've got, the pan you're using, and the way you're heating it.
It's not High though lol
I never had all the spitting and overflowing issues people talk about, but I heated it somewhat slowly;
Took something like an 45-60 minutes to caramelize the honey to where I wanted it.
Meadmakers are unique in that some of them come from wine making and some come from home brewing.. So the whole dilute-boil down thing, that's a beer makers / wort making technique that isn't necessary unless you add too much water. Dont need to make it any harder than it already is.
The Banana-infused Brandy; I bought ~20 pounds of bananas and let them sit out until the peels were more black than any other color; I bought 1/2 gallon of E&J VSOP brandy. I took a 1-gallon jug, with accompanying airlock and bung, and poured in the 1/2 gallon of brandy. I then peeled the black-peel bananas, cut them into pieces and added the flesh of the fruit to the brandy until the 1-gallon jug was full. I'm pretty sure I added a little k-meta to the jug before the brandy, just to preserve the color of the bananas over time. This mixture sat for ~3 months.
Then strained the banana solids out, and ended up with the original 1/2 gallon + 375ml bottle full;
The 1/2 gallon went into the 3-gallon batch;
The 375ml was delicious all by itself.