Cook the Pasta: Bring a large pot of salted water to a boil. Add the penne pasta and cook until al dente according to the package instructions. Drain and set aside.

Prepare the Creamy Sauce: In a large saucepan, melt 25g of butter over medium heat. Add the diced onion and sauté until softened. Stir in the cream, sour cream, mayonnaise, and season with a pinch of salt and pepper. Cook until heated through.

Add the Tuna and Corn: Gently fold in the drained tuna, corn kernels, and sliced shallots. Mix well and set the sauce aside.

Make the Cheese Sauce: In a separate saucepan, melt the extra 60g butter over medium heat. Stir in the flour and cook for 1 minute, stirring constantly. Gradually whisk in the milk and cook until the mixture thickens. Remove from heat and stir in 1½ cups of grated cheese, reserving ½ cup for topping.

Assemble the Bake: Preheat the oven to 200°C (390°F). Grease a large baking dish. Combine the cooked pasta with the creamy tuna mixture and transfer to the prepared baking dish. Pour the cheese sauce evenly over the top and sprinkle with the remaining grated cheese.

Bake: Place the dish in the preheated oven and bake for 20-25 minutes, or until the top is golden and bubbly.

Serve: Allow the bake to rest for 5 minutes before serving. Pair it with a fresh salad or steamed vegetables for a balanced meal.