Preheat and Prep: First, preheat your oven to 220°C (200°C fan). Pour the 115g of melted unsalted butter into a 20cm (8-inch) square baking dish, ensuring the entire bottom is covered. Set it aside.

Combine Dry Ingredients: In a large mixing bowl, whisk together the plain flour, caster sugar, baking powder, salt, black pepper, and garlic powder. This ensures all the leavening agents and seasonings are evenly distributed.

Add Cheese and Ham: Add the grated cheddar, diced ham, and chopped chives (if using) to the dry ingredients. Toss everything together with your fingers until the ham and cheese are coated in the flour mixture. This prevents them from sinking to the bottom of the biscuits.

Form the Dough: Pour the buttermilk into the bowl. Using a spatula or wooden spoon, mix until a shaggy, soft dough forms. It's crucial not to overmix here; stop as soon as there are no large pockets of dry flour remaining.

Shape the Biscuits: Turn the dough out onto a lightly floured surface and gently pat it into a rough square, about 2cm thick. I find that patting it with my hands is much better than using a rolling pin, as it keeps the dough tender. Cut the dough into 9 equal squares.

Arrange in the Pan: Carefully place each square of dough into the prepared baking dish with the melted butter. The butter will come up the sides of the dough. Arrange the squares so they are just touching.

Bake to Perfection: Place the dish in the preheated oven and bake for 20-25 minutes. The biscuits are done when they are tall, deeply golden brown on top, and the edges are bubbling in the butter.

Cool and Serve: Let the biscuits cool in the pan for about 5-10 minutes before serving. This allows them to set up slightly and makes them easier to remove. They are best served warm.