Heat beer, shredded cheddar cheese, and crushed garlic in a fondue pot.

Cook gently over low heat, stirring constantly, until the cheese has melted.

Stir in the butter.

Blend cornflour with a little water to form a slurry.

Add the cornflour slurry to the fondue pot.

Add the whole grain mustard.

Continue cooking, stirring constantly, until the fondue has thickened.

Season with ground black pepper to taste.

Transfer the fondue pot to a burner.

Serve the fondue with cubed onion bread, cubed cooked chicken, cubed ham, and a small dish of chutney for dipping.