Heat oven to 400 degrees F. On rimmed baking sheet, toss cauliflower florets with 2 teaspoons fresh thyme leaves, 1 tablespoon olive oil and a sprinkle of salt and pepper. Roast 30 to 40 minutes, stirring occasionally, until softened and browned.

Meanwhile, melt butter in medium skillet over medium-high heat. Add sliced leeks, mushrooms and more salt and pepper to taste. Cook, stirring often, 5 to 8 minutes until leeks and mushrooms are softened.

Increase oven temperature to 450 degrees F. Brush 2 rimmed baking sheets with olive oil; sprinkle lightly with cornmeal. Press 1 ball of pizza dough on each baking sheet into 12-inch round.

In small bowl, whisk remaining 2 teaspoons olive oil and minced garlic. Spoon or brush over pizzas. Sprinkle each pizza with 1 cup shredded cheese, then top evenly with roasted cauliflower, leek-mushroom mixture and remaining 1 tablespoon fresh thyme leaves. Top each pizza with remaining 1/2 cup cheese.

Carefully fold top third of 1 pizza dough down, then fold bottom third of pizza dough up. Press and pinch seam to seal. Press and fold over shorter edges of dough to seal. Repeat with remaining pizza.

Bake pizzas 20 to 25 minutes until crust is baked through and golden brown, rotating sheets halfway through baking. Let pizzas cool 5 minutes before slicing.