For the cauliflower: Preheat the oven to 350 degrees F.
Trim the green leaves from the base of each head of cauliflower. Then trim a sliver off of each base to level it. Make 2 equal slices vertically from the top to the base of each head of cauliflower, creating 4 steaks in total.
In a large baking dish, add the beer, brown sugar, Worcestershire sauce, red chile flakes, garlic, a nice pinch of salt and a few grinds of black pepper. Whisk until the sugar and salt dissolve, then place the steaks in 1 layer in the dish.
Bake the steaks, flipping them once, until tender but still firm enough to hold their shape, about 20 minutes. Use your judgment when you flip them to determine if they need to cook the full 20 minutes.
Transfer the cauliflower steaks to a paper towel-lined baking sheet; reserve the baking liquid for the next step. Pat the top of each steak dry as well.
For the glaze: In a medium bowl, add the jam, jerk seasoning, lime juice and 1/4 cup of the cauliflower baking liquid. Stir to loosen and combine.
Heat a cast-iron griddle to medium-high heat (cast iron is preferred, but you can use a large pan and do this in batches, or use a nonstick griddle, but cast iron--ooooh--cast iron!!!).
Drizzle each cauliflower steak with olive oil on both sides followed by a pinch of salt and a few grinds of pepper. Place the steaks on the griddle and cook until lightly golden brown when you take a peek beneath, 4 to 6 minutes; gently flip the steaks, then allow them to become golden brown again on the other side. Brush the tops and sides of each liberally with the glaze. Cook for 2 to 3 minutes more, then remove to a platter and sprinkle with the mint and cilantro. Serve warm.
Chop the chilled leftovers for a quick salad.