Cauliflower Steaks with Maitake Mushrooms and Browned Butter-Caper Sauce

Almost a full-fledged dish and absolutely satisfying-a dish using a knife and fork, emphasizing vegetables. Maitake mushrooms, also known as wild chicken, have a rich nutty taste, which especially complements the dish. If you can't find them, add a handful of your other favorite mushrooms.
Place the jelly roll pan in the oven. Preheat the oven to 450 ° (leave the baking sheet in the oven).Put 1 1/2 teaspoons of butter and minced garlic in a small bowl suitable for a microwave oven. Reheat in the microwave at MEDIUM power (50%) for 1 minute or until the butter melts and the garlic is fragrant. Cool slightly; discard the garlic.Carefully cut 2 "steaks" 1-inch thick vertically from the center of each cauliflower head; reserve the remaining cauliflower for another use. Carefully trim the maitake bottoms, keeping the mushroom lumps intact. Carefully cut each maitake lengthwise in half. Brush the tops of the cauliflower steaks with the butter mixture. Carefully place the cauliflower steaks, buttered sides down, in a preheated skillet; brush the tops of the steaks with the butter mixture. Bake at 450 ° C for 14 minutes or until the bottoms are lightly browned. Remove the baking tray from the oven; gently flip the cauliflower steaks. Gently brush the remaining butter mixture over the maitake steaks on both sides; place in the pan with the cauliflower cut side down. Bake at 450 ° C for 13 minutes or until the cauliflower is browned and cooked through. Remove from the oven; sprinkle evenly with 1/4 teaspoon salt and 1/4 teaspoon pepper.While the cauliflower is baking, bring the milk and 1/2 cup water to a boil. Gradually add the polenta, stirring constantly with a whisk. Cook for 3 minutes or until thickened, stirring constantly. Add the remaining 1/2 teaspoon salt. Cover and keep warm.Melt the remaining 2 tablespoons of butter in a medium skillet over medium-high heat; cook for 3 minutes or until lightly browned and very fragrant. Add the chopped garlic; cook for 45 seconds, stirring frequently. Add the wine; increase the heat to medium-high and cook for 1 minute or until about half of the liquid has evaporated. Combine the broth and flour, stirring with a whisk. Add the stock mixture to the pan; bring to a boil. Cook for 1 minute or until slightly thickened, stirring constantly; add the capers, juice, thyme, and remaining 1/4 teaspoon pepper. Place approximately 3/4 cup polenta on each of the 4 plates. For each serving, add 1 cauliflower steak, 1 maitake steak, and about 2 tablespoons of sauce. Garnish with thyme if desired.