Heat your frying pan over medium heat. Add the minced beef and cook until browned. Break up any large lumps with your spoon. Drain any excess fat from the pan now.

Stir in the chopped onions and crushed garlic. Cook them with the beef for five minutes. The onions should become soft and translucent. This creates a sweet flavor base.

Add the chopped tomatoes and tomato purée. Crumble in the stock cube and add oregano. Let it simmer for fifteen minutes. The sauce should be thick and rich.

Melt butter in a separate saucepan. Stir in the flour to make a paste. Gradually whisk in the milk over medium heat. Keep whisking until the sauce is thick and smooth.

Remove the white sauce from the heat. Stir in the mustard and half of the Cheddar cheese. Season with a little salt and pepper. This sauce adds a lovely creamy layer.

Wait for the meat mixture to cool slightly. Use a small spoon to stuff the tubes. You can also use a piping bag for speed. Do not overstuff them or they might crack.

Spread a little meat sauce on the dish bottom. Lay the filled tubes in a single row. Pour the creamy white sauce over the top. Ensure all the pasta is completely covered.

Sprinkle the remaining Cheddar and Parmesan over the top. The Parmesan creates a lovely golden crust. This is the secret to a professional-looking finish.

Place the dish in a preheated oven at 200°C. Bake for thirty-five to forty minutes. The top should be bubbly and brown. The pasta should feel soft when poked.

Remove the cannelloni from the oven. Let it sit for five minutes before serving. This helps the layers set properly. It makes it much easier to serve neat portions.