Heat the butter and olive oil in a pan.
Saute the garlic for about 30 seconds.
Add the mushroom halves to the sauteed garlic. Sprinkle lightly with salt and pepper. Cook over medium heat, stirring often, for about a minute.
Throw in the cauliflower florets. Sprinkle with a little more salt and pepper. Cook, stirring, for a minute.
Pour in a tablespoon or so of water. Not a lot. Just enough to create steam. Cover the pan and let the cauliflower and mushrooms cook in the steam.
Scoop out the mushrooms and cauliflower and transfer to a shallow bowl or bowls.
Stir together the balsamic vinegar and extra virgin olive oil. Drizzle over the mushrooms and cauliflower.
Garnish the garlicky mushrooms and cauliflower with balsamic vinaigrette with toasted nuts and chopped parsley before serving.