Finely slice the fennel and celery, then mince the 3 garlic cloves.

Heat 1 tablespoon olive oil in a large frying pan, then sauté the fennel, celery, garlic, and salt for about 5 minutes.

Pour in the 350 ml vegan white wine, then simmer uncovered for 10 minutes.

Add the crushed tomatoes and orange zest, then cover and simmer for 10 minutes.

Preheat the oven to 180°C / 350°F, then drain the white beans and red peppers if needed.

Stir the white beans, red peppers, olives, and fresh oregano into the sauce, then transfer the mixture to the baking dish.

Combine breadcrumbs, almond flour, nutritional yeast, fennel seeds, Herbes de Provence, black pepper, and the remaining olive oil in a bowl, then mix until crumbly.

Scatter the breadcrumb mixture evenly over the gratin, then bake for 30 minutes until crisp and golden.