Preparation Steps

• Preheat the oven to 375°F. Lightly oil a 9x9-inch baking dish and set aside.
• Bring a large pot of salted water to a boil. Cook the pasta just until al dente according to package directions (check 1–2 minutes before the minimum time). Drain, rinse briefly with warm water to stop cooking, and transfer to a large mixing bowl.
• While the pasta cooks, heat the olive oil in a large skillet over medium heat. Add the chopped onion and sliced mushrooms; sauté until the onion is translucent and the mushrooms release their liquid, about 6–8 minutes.
• Stir in the minced garlic and cook 1 minute more until fragrant. Sprinkle the flour over the vegetables and stir thoroughly so the flour absorbs the pan juices and lightly toasts, about 1 minute.
• Slowly whisk in the almond milk and vegetable broth, scraping up any browned bits. Bring the mixture to a gentle simmer, then lower the heat and cook, stirring occasionally, until the sauce thickens and coats the back of a spoon, about 8–10 minutes.
• Remove the pan from heat and whisk in the shredded cheddar and Dijon until fully incorporated. Season to taste with salt and pepper.
• Fold the drained tuna (flaked), cooked pasta, and frozen peas into the sauce until everything is evenly coated. Transfer the mixture to the prepared baking dish and smooth the surface.
• Combine the Parmesan and panko (or almond meal) in a small bowl and sprinkle evenly over the casserole. For extra crunch and color, drizzle a little olive oil over the crumbs.
• Bake at 375°F for 18–22 minutes, until the edges bubble and the topping is golden. If you want a deeper brown crust, broil for 1–2 minutes — watch closely to avoid burning.
• Let the casserole rest for 5 minutes before serving so slices set slightly. Serve warm.