Preheat the oven to 375°F (190°C). In a bowl, mix together the panko breadcrumbs, grated Parmesan cheese, parsley, garlic powder, salt, and black pepper. Form the Boursin cheese into a round or oval shape and coat it in the breadcrumb mixture. Place it on a baking sheet and bake for 15-20 minutes until golden brown.

Make the Onion Toast

Cook the Onions

In a skillet, heat the olive oil and butter over medium heat. Add the thinly sliced onion and cook until caramelized, about 15 minutes, stirring occasionally. Toast the sourdough slices until golden brown.

Prepare the House Preserves

Make the Berry Preserves

In a saucepan, combine the mixed berries, sugar, and lemon juice. Cook over medium heat for 10-15 minutes until the berries break down and the mixture thickens. Let it cool before serving.

Fry the Leeks

Make Crispy Leeks

Dredge the thinly sliced leeks in flour, shaking off the excess. Heat vegetable oil in a deep pan over medium-high heat. Fry the leeks in batches until golden and crispy, about 2-3 minutes. Drain on paper towels and season with salt.

Serve

Assemble the Dish

On a plate, arrange the toasted sourdough, top with caramelized onions, a slice of the crusted Boursin cheese, a dollop of house preserves, and garnish with crispy leeks.