Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a large mixing bowl, whisk together self-rising flour and baking soda until combined.

Cut the very cold, cubed butter into the flour mixture until it resembles coarse crumbs.

Make a well in the flour mixture and pour in the cold buttermilk, stirring gently until just combined.

Transfer the dough to a floured surface, shape into a rectangle about 1 inch thick, then fold into thirds and roll out to ½-inch thickness.

Sprinkle half of the grated Irish cheddar cheese and chopped green onions onto the rolled-out dough, fold over and roll out again.

Cut out biscuits using a 2- to 3-inch round cutter and place on the prepared baking sheet.

Brush the tops of the biscuits with buttermilk and bake for about 20 minutes until golden brown.