Combine all the breadcrumb topping ingredients in a small bowl and set aside.
Boil water, cook pasta, drain and set aside.
Melt butter, whisk in garlic and flour, slowly add milk and whisk until thickened.
Add vegetable stock powder, onion powder, mustard, parmesan, tuna, corn, broccoli, and pasta to the white sauce and stir well.
Pour the tuna mix into a baking dish, top with cheese and breadcrumb topping.
Bake at 180C fan for 30 minutes, then remove foil and bake for an additional 15 minutes.