Makes about 2 cups
Combine the mushrooms and andouille in the bowl of a food processor and pulse about 10 times, until the mixture forms a coarse paste.
Heat oil in a medium skillet over high heat. Add onion and garlic, Essence, salt, and pepper, and saute, stirring occasionally, for about 2 minutes. Add mushroom-sausage mixture and cook, stirring occasionally, for another 2 minutes. Stir in port and cook for 1 minute longer.
Reduce heat to medium, add breadcrumbs, and cook, stirring constantly, for 2 minutes. Remove from heat and allow to cool before using.
Note: Remove crusts from a dense, homemade-type white bread, and crumb 3 or 4 slices at a time in a food processor or blender. Store in an airtight container at room temperature for up to 3 days.