Pre heat your oven to 200c.
Add your sliced onion to a pan with some rapeseed oil and cook on medium for 5 minutes until softened. Next add the balsamic vinegar and stir well, turning the heat down to low. Cook for a further 10 minutes, stirring often. Remove from heat and set aside.
In a bowl add the flour, baking powder and oregano. Season generously with salt and pepper, and stir until well combined.
Add the cubed butter to the bowl. Rub the butter and flour together with your finger tips until a crumb is formed. Stop when the crumb is even and you have no large chunks of butter left.
Add to the bowl the cooled caramelised onions, olives and 100g of grated cheddar and mix until evenly combined. Use a wooden spoon to mix - your hands may melt the butter.
Stir in the milk until a dough has formed and turn out onto a clean, floured surface. Knead the dough until it comes together to form a moist but firm dough.
Roll the dough out to 2 cm thick. Use your cutter to cut out the scone shapes, and place them onto a lined baking tray. Gather up any leftovers, roll once more and cut more scone shapes. Repeat until the dough is used up.
Wash the top of your scones with some milk and then sprinkle the rest of the grated grated cheese over the top of each scone.
Place in the oven for 15 minutes until risen and golden brown with a bubbly cheesy topping.