Clean the mushrooms with a wet paper towel. Twist to separate the caps from the stems. Place the caps on a cookie sheet.
Put all of the stems in a food processor. Coarsely chop the stems.
Mince the garlic cloves.
Heat a tsp of olive oil in a saute pan over medium heat. Add the garlic and the chopped stems.
Roughly chop the parsley by hand or in the food processor.
Once the mushrooms start to release moisture (around 2 minutes), add parsley to the pan.
Add the pine nuts and breadcrumbs a few tablespoons at a time. You should also add more olive oil at this time to keep the mixture from getting too dry. Keep adding until it's moist, without being too dry or too wet. Turn the heat off.
After a few minutes of cooling, add parmesan and romano cheese. Stir to incorporate.
Preheat the oven to 350 degrees.
Take a small spoonful of filling and add it to one mushroom cap at a time. *I usually fill them conservatively at first, and then add more depending on how much filling I have left.
Place all of the filled mushrooms on a lined cookie sheet and bake for 20 minutes, or until fork tender.