Rinse tofu under cold water and slice in half lengthwise. Wrap in a double layer of paper towels and place on a plate. Place a second plate on top and let sit at least 15 minutes to press out excess water.

Meanwhile, steam or microwave cauliflower according to package directions until very tender. Using a food processor or potato masher, mash cauliflower with milk, garlic, butter, thyme, ½ teaspoon salt, and ¼ teaspoon pepper until smooth. Cover to keep warm.

On a plate, mix chia seeds, cayenne, lime zest, and remaining salt and pepper. Slice tofu pieces crosswise to yield four blocks. Brush each side with sesame oil. Press each side of tofu into chia mixture to coat thoroughly.

Heat vegetable oil in a skillet over medium heat. Sear tofu blocks until crisp and golden brown, about 5 minutes on each side. Serve at once with cauliflower mash.