Preheat the oven to 425°F.
Line a baking sheet with parchment paper or aluminum foil. Alternatively, you can butter the baking sheet and dust it lightly with flour. Set aside.
In a large mixing bowl, whisk together the flour, sugar, salt, and baking soda.
Add the butter to the flour mixture, and work it into the flour with your hands until the mixture resembles damp sand. (See video.)
Add the currants or other dried fruit to the flour and butter mixture, and mix well so that the fruit is completely coated with the flour.
Add the egg to the buttermilk and mix well.
Make a well in the flour and butter mixture and pour in the egg buttermilk mixture.
Forming your hand into an open claw shape, mix everything together so that the flour and butter mixture is completely saturated with the egg buttermilk mixture and begins to come together and hold its shape. Use a light hand to mix this dough, and DO NOT knead the dough. (See video.) If the mixture is very sticky, you can add up to 1/4 cup of all-purpose flour.
Gently form the dough into a ball in the bowl.
Transfer the ball to the baking sheet.
Dust hands lightly with flour and pat the dough ball down gently to flatten slightly.
Using a sharp or serrated knife, cut a large cross across the top of the dough. (See video.)
Make a small indentation in each quadrant of the dough with the tip of the knife.
Transfer the baking sheet with the dough onto the middle rack of the preheated oven.
Bake until the bread is golden brown, and when tapped on the bottom, the bread sounds hollow. The baking process takes approximately 35-45 minutes.
If the bread is browning too quickly, but has not yet finished baking, you can tent it with foil.
When the bread has baked thoroughly, remove the baking sheet with the bread from the oven and place it on a heatproof surface.
Transfer the bread to a cooling rack, and allow the bread to cool for 10 minutes before slicing. Bread may be served warm or at room temperature.
Whole Wheat Irish Soda Bread can be stored in the refrigerator, well wrapped, for 3-4 days. It can also be stored in the freezer, well wrapped, for 2-3 months.