1 head cauliflower, cut into florets
1 container (6 ounces) 0% plain Greek yogurt
1 tablespoon butter
2 garlic cloves, roughly chopped
2 tablespoons chopped fresh dill, plus additional for garnish
2 tablespoons chopped fresh flat-leaf parsley, plus additional for garnish
Kosher salt and freshly ground black pepper
2 tablespoons finely grated Parmigiano-Reggiano cheese