Cook the white onion in the olive oil. When it is soft add the balsamic vinegar and light brown sugar. Let it simmer for around 15 minutes. Remove from the heat and set aside to cool
Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4
Sieve the plain flour into a bowl and add the bicarbonate of soda and salt, stir together
Mix the cheese and the cooled onion into the flour mixture
Add the buttermilk to the flour and bring it together to make a dough. Work it as little as needed. Shape it into a ball on a baking tray dusted with flour and cut a cross down in the centre, cut deeply, almost to the bottom but not all the way through. Top with the extra cheese
Bake the loaf for 30-40 minutes. When it sounds hollow when tapped on the bottom it's done
Cool on a rack, you can eat it warm or wait till it cools, store in an airtight container and it's best eaten within 1-2 days, but will last 3 days
Notes
You should only use regular plain flour for this recipe (also known as all purpose flour). Do not use strong bread flour, as this will make the soda bread very dense.
I used balsamic vinegar and light brown soft sugar for caramelising the onions. You can swap these out for red wine vinegar and caster or granulated sugar.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.