Preheat oven to 375º F.
Heat olive oil in a pan over medium heat. To avoid waste and add flavor, you can use the olive oil from the tin of sardines!
Pop the onions, mushrooms, and garlic into the pan. Simmer for about 2 minutes or until they've softened.
Stir the capers, olives, and sardines into the pan and and break down the caper berries with your spatula or spoon as your stir. Let them warm in the pan for about a minute, then remove the pan from the heat. Transfer the mixture to a mixing bowl.
Add the goat cheese to the bowl and stir until the cheese melts into the mixture and is blended in; set aside.
Place the peppers on a cast iron pan open side down. Lightly brush the backs of the peppers with a bit of olive oil, then flip them over.
Scoop the mixture into the peppers until they're filled to the brim.
Sprinkle panko breadcrumbs over the peppers, pop them into the oven, and lwt them bake for 20 minutes.
When done, remove the peppers from the oven and sprinkle the lemon zest and fresh chopped parsley over the peppers. Serve with lemon wedges.