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.
While the cauliflower is cooking, make the sauce. Heat 1 teaspoon of oil in a pan and add the shallots. Cook them for about 5 minutes, until they begin to brown. Add the ginger, garlic, and chilies. Cook for a minute or two and then add the scallions and the lime juice, tamari, and agave. Cook for another minute or two, remove from the heat, and add the cilantro and peanuts.
When the cauliflower is ready, heat the remaining teaspoon of oil in a large pan over medium-high heat. Gently place the cauliflower steaks in the pan. Let them cook for about 4 to 6 minutes on each side, until they're golden-brown. Don’t fuss with them too much, or they will fall apart.
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 shallot-lime sauce. Repeat with the rest of the cauliflower.