In a large mixing bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of baking powder, ½ teaspoon of baking soda, 1 tablespoon of sugar, and 1 teaspoon of kosher salt until well combined.

In a separate bowl, combine 1 tablespoon of Dijon mustard and ¾ cup of chilled Irish stout. Stir until smooth.

Grate the frozen Irish butter directly into the flour mixture, tossing gently until each piece is coated.

Add 1 cup of grated aged Irish cheddar to the mixture, create a well in the center, and pour in the stout and mustard mixture. Gently fold together until just combined.

On a lightly floured surface, turn out the shaggy dough and knead a couple of times. Roll out to about 1-inch thick and fold it over a few times.

Form the dough into a square, cut into squares or rounds, and place on a parchment-lined baking sheet. Freeze for at least 15 minutes.

Preheat your oven to 425°F (220°C). Brush the tops of the biscuits with melted butter and sprinkle lightly with sea salt. Bake for 18-22 minutes or until golden brown.