SautÃ© onions and garlic in oil until soft and transparent, add the mushrooms and all the seasonings.
Continue to cook slowly until the mushrooms begin to release their juices, remove from the heat and allow to cool for 5 minutes. Next add the stuffing mix and stir well.
In a food processor combine the parmesan cheese, cream cheese and ricotta cheese, add the cooled mushroom mixture, and continue to process until all the ingredients are combined but still slightly coarse, season to taste.
Butter the inside of a 2 pint oven proof mould or 6 individual ramekins and place a piece of wax paper or parchment on the bottom. Pour in the mushroom pate and tamp down to remove any air bubbles.
Bake in the centre part of the oven at 400%F for about one hour. Remove from the oven and allow to cool, cover the top with a piece of wax paper and place some weights on top.
Refrigerate for at least 24 hours prior to serving. To serve, remove the wax paper and blot off any surfaces juices before turning onto a platter.