Wash and dry the zucchini thoroughly, then trim the ends. Slice each vegetable lengthwise into thick slabs, aiming for about half an inch in thickness to ensure they stay sturdy during roasting.
Use a sharp knife to cut a shallow crosshatch pattern into the top of each slice, being careful not to cut through the skin. This creates channels for the garlic butter to seep deep into the zucchini for maximum flavor.
Brush the zucchini with a mixture of melted butter, minced garlic, and herbs, making sure to fill the cuts. Place them on a lined baking sheet and roast at 400°F until the edges start to turn golden and the center is tender.
Remove the pan from the oven and pile a blend of mozzarella and Parmesan cheese onto each steak. Switch the oven to the broil setting and return the pan to the heat for a few minutes until the cheese is bubbly and browned.
Let the steaks rest for a few minutes so the cheese can set, then sprinkle with fresh basil before serving.
