Preheat the oven to 350ºF.
In a large bowl, whisk together the filler ingredients. Stir in the shredded mushroom, then mix in the breadcrumbs. Shape the mixture into 6 cakes, pressing firmly.
Heat olive oil in a pan over medium-high heat, cook the cakes for 3-4 minutes, then transfer the pan to the oven for 10 minutes. Broil at 500ºF for 2 minutes.
Plate and serve with your preferred sauce and garnishes. We used remoulade and a slice of lemon.