Preheat the oven to 350°F.
With the cauliflower sitting on its stem, slice it into large slabs, about 1-inch thick. Slice it the same way you would slice a loaf of bread. You’ll get two or three large slabs.
Mix together the vegetable stock, garlic, lemongrass, and kaffir lime leaves, if using, in a 9x12-inch baking dish.
Place the cauliflower in the dish with the stock mixture and cover tightly with foil. Bake for about 40 minutes, or a knife can go into it easily. It should be cooked throughout but still a little firm.
Heat 1 teaspoon of oil in a large fry pan over medium-high heat. Gently place the cauliflower steaks in the pan. Let it cook for about 4 to 6 minutes on each side. You want to get it golden brown. Don’t fuss with it too much, or it will fall apart.
Set the cauliflower aside and keep warm.
Mix together the lime juice, tamari, and agave.
Add the rest of the oil to the pan along with the shallots. Let cook for about 5 minutes, until it begins to brown and is fragrant. Add the ginger, garlic, and chilies. Cook for a minute or two and then add the scallions and the lime juice mixture. Cook for another minute, remove from the heat, and the cilantro and peanuts.
To serve, place a spoonful or two of the Spicy Peanut Sauce at the bottom of a shallow bowl or plate. Place one of the cauliflower steaks in the center and then top with the warm shallot-lime sauce. Repeat with the rest of the steaks.