To a small bowl, mix together the raisins and Irish whiskey. Cover with plastic wrap and allow to macerate overnight or at least 6 hours. Drain the raisins, reserving the Irish whiskey/raisin liquid for making a syrup (if you like!) later on in the recipe. Set both aside.
Preheat the oven to 425 degrees F. Line a baking sheet with parchment; set aside. (You could also bake this bread in a cast iron skillet, if you like. Be sure the skillet is seasoned and lightly greased so the bottom won't stick.)
In a large mixing bowl, whisk together the all-purpose flour, whole wheat pastry flour, brown sugar, salt and baking soda. Using a box grater, grate the butter into the dry ingredients and mix quickly, being sure the butter is broken up into pea-sized bits. Next, add the raisins and toss them gently in the flour mixture so they are evenly distributed.
Create a well in the center of the flour mixture and pour in the buttermilk. Using a wooden spoon, mix it together until it forms a shaggy ball. Drop the soda bread dough onto a lightly floured counter and knead a few times, being sure to not over handle it, which will result in tough bread. Form the soda bread into a 1 1/2-inch thick disc. Using a knife, score the top, forming an X, and brush it with buttermilk.
Transfer the soda bread to the baking sheet and bake for 40-45 minutes, and until a skewer inserted into the center comes out clean. Serve warm with plenty of butter, a sprinkling of sea salt and maybe the whiskey/raisin sauce that is below.
