Roast the Garlic: slice off the top of the head of garlic to expose the cloves. Heat a small skillet to low heat and add olive oil. Place the garlic "cut-side" down and cover with a lid. Cook for 10-15 minutes, checking occasionally (during this time you can start on the dough). Remove from heat, let cool slightly, then squeeze out and mash cloves.
Preheat the oven to 375 F (190 C).
(Optional) If making your own buttermilk, mix the milk and acid together and let sit while you complete the next 3 steps.
In a large bowl, whisk together the flour, salt, baking soda, and sugar (if using).
Stir in the chopped rosemary and grated cheddar.
Once the mashed roasted garlic is ready, add it and mix gently to evenly distribute.
Pour in the buttermilk until a slightly sticky dough forms. If the dough is still too crumbly, you can add more milk/buttermilk (recommended) or water.
Turn the dough out onto a floured surface and shape into a round loaf.
Transfer the loaf to a parchment-lined baking sheet and score a ½ inch (1-1¼ cm) deep cross into the bread to “let the fairies out”.
Bake for 40-45 minutes until golden.
Cool on a wire rack for at least 20 minutes before slicing.
