Preheat the oven to 180°C / 160°C fan / gas mark 4.
Cook the pasta according to the packet instructions, then drain and set aside.
In a saucepan, melt the dairy-free butter over a medium heat.
Stir in the plain flour and cook for 1 minute, stirring constantly.
Gradually add the dairy-free milk, stirring well to keep the sauce smooth.
Add the oat cream, dairy-free grated cheese, nutritional yeast, and Dijon mustard.
Stir until the sauce is smooth and creamy, then season with salt and pepper.
Add the cooked pasta and stir until fully coated.
Transfer to an ovenproof dish and sprinkle over the breadcrumbs if using.
Bake for 15 minutes until hot through and lightly golden on top.
Serve warm.