The secret to a good doughnut sandwich is excess.
You think cheese will be too much?
Better use two different kinds.
The glaze is enough sweetness on its own, right?
It will be once you add a long draw of syrup.
I cannot toast a doughnut in butter.
Yes. Yes you can.
You're making a sandwich out of a doughnut. There's no hope left for you anymore. Just totally submit yourself to the spirit of the dish. The greasy, heavy, toasty, sticky spirit of the dish. You can repent after your meal.*
*Which I would suggest actually doing, because there's no way consuming something as delicious as this isn't at some level unrighteous.
Sammich #1: glazed doughnut + veggie cold cut + golden syrup + fried egg + sharp white cheddar + cream cheese
Sammich #2: maple glazed doughnut + thick cream cheese + apricot preserves + hickory smoked veggie cold cuts