Preparation

1. Preheat oven to 400F. Line a small sheet pan with parchment paper. Toast Nuts: Place pecans on prepared sheet pan and place in oven. Toast nuts 3 minutes or until fragrant. Set aside to cool and place in a small bowl or saucer until ready to chop. Lightly oil the parchment paper on the same sheet pan for the mushrooms.
2. Trim the bottoms of the mushroom stems and discard. Remove and reserve the stems from the mushroom caps and set aside. Arrange the mushroom caps, gill side up, on the prepared sheet pan and roast in the preheated oven for 10 minutes or until they soften a little and accumulate juices. Reserve the juices! Allow to cool on the sheet pan.
3. Chop the pecans in the bowl of a food processor, pulsing to chop to get small pieces, but not too fine. Remove and set aside. Chop the reserved stems in the bowl of a food processor, pulsing to chop.
4. Warm the olive oil over medium heat in a non-stick pan and saute the shallots for about 3 minutes, add the garlic and saute an additional minute or until the garlic becomes translucent. Add the chopped mushrooms and reserved juices and sherry or vegetable stock and cook until most of their moisture evaporates, stirring frequently. Remove from heat then add the toasted pecans, bread crumbs, cheese, chopped parsley, salt and pepper. Stir to combine.
5. Generously stuff the mushroom caps, piling the stuffing into a mound above the caps. When ready to serve, bring to room temperature and re-heat them in a 400F oven for about 10 minutes. Serve warm.