Burger's Priest is my favourite burger joint in Toronto. I absolutely love the deep-fried breaded portobello mushrooms + cheese, or as they refer to it: The "Option." My go-to burger there is The Priest, which is a cheeseburger + the "Option." I've also tried just the "Option" as well as the Religious Hyprocrite (the "Option" + bacon). Both were delicious, but I missed the beef patty.
Some of the burgers from the "Secret Menu" (which is not so secret anymore as it's posted on their website now) are pretty costly. But then again, some of them are a behemoth of a burger and are more novelty items than anything, so maybe that justifies the price.
Be warned, there's not much seating inside. Your best bet is to grab your food, and go find a bench nearby to eat. And I wasn't a huge fan of the fries, but if you're like me, you go there for the burgers so that's really not a problem.
So, if you're in the mood for burgers, I'd give this place a try. And if you're feeling adventurous and hungry and aren't at risk for a heart attack, you could even try The Four Horsemen of the Apocalypse (2 options, 2 beef patties, and 2 grilled cheese sandwiches instead of buns).