Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
Slice the cauliflower into thick steaks (about 1-inch thick) and reserve any loose florets for a side dish or addition to the sauce.
Pat the tofu dry and cut it into ½-inch thick slices. In a small bowl, lightly beat the egg.
Set up a dipping station: Place the beaten egg in one shallow dish and spread sesame seeds in another.
Dip each tofu slice first in the egg, then coat with sesame seeds to form a crispy crust.
Heat olive oil in a large skillet over medium-high heat. Sear the tofu slices for 2-3 minutes on each side until golden. Remove and set aside.
Lightly brush both sides of the cauliflower steaks with olive oil. Season with a pinch of salt and pepper if desired.
Place the cauliflower steaks on the prepared baking sheet and roast in the oven for 20-25 minutes, flipping halfway through, until edges are crisp and tender.
Meanwhile, prepare the ginger-miso sauce: In a small bowl, whisk together miso paste, rice vinegar, soy sauce, grated ginger, and minced garlic until smooth. If desired, add a splash of warm water to reach a drizzling consistency.
Once the cauliflower is roasted, serve the steaks on a plate, top with seared tofu slices, and generously drizzle the ginger-miso sauce over the dish.
Garnish with extra sesame seeds if desired and enjoy your nutritious, flavorful meal.