Yah, most small high speed ferrite transformers fall over at about 300kHz, this is why I was going to first boost the voltage, convert to high voltage DC and switch it back into a square wave, I'm just not sure on how to switch it with both high voltage and high frequency. I'm pretty sure i'd be fine if it were one or the other but combined they make it much more difficult for my simple brain.

It's for an experimental rf heating device.

Thanks