Preheat the oven to 375°F. Line a large baking sheet with parchment paper.
In a bowl, toss together the shredded gruyere, parmesan, dried thyme, black pepper, and garlic powder until the cheese is evenly seasoned.
Place heaping tablespoon-sized mounds of the cheese mixture on the prepared baking sheet, leaving about 2 inches between each mound. Flatten them slightly and press a few pieces of chopped walnut into the top of each one.
Bake for 6 to 8 minutes, until the cheese is bubbling vigorously and the edges are a deep, rich golden brown.
Remove from the oven and let the bites cool on the baking sheet for at least 5 minutes. They will go from soft and flexible to crispy and crunchy as they cool. The walnut adds a beautiful toasty crunch. Serve at room temperature.