Pre- heat oven to 425. Line baking sheet with parchment paper or foil.
Clean the mushrooms and remove the stems. Place on prepared baking sheet. Mix olive oil with minced garlic together and brush the mushroom caps on both sides.
Turn the mushroom cap top down and drizzle them with balsamic vinegar. Sprinkle with salt and pepper. Roast for about 15 minutes. Remove from oven and place a small spoonful of blue cheese into each mushroom. Return to the oven for another 5 minutes.
Place mushrooms on platter, sprinkle with pecan pieces (or toasted pine nuts), basil and additional balsamic vinegar if desired.