Clean at least 12 large mushrooms and remove the stems. Leave the caps aside to be stuffed, and chop the stems for part of the stuffing and dice 1/2 an onion.
In Bertolli Extra Virgin Olive Oil saute the chopped stems, chopped pecans, breadcrumbs, and a minced clove of garlic. Now add a teaspoon of lemon juice and salt and pepper to taste. Add a little more olive oil if the mixture is too dry.
Now spoon the stuffing into the caps and place them in a non-stick, oven proof pan.