Preheat the oven to 375°F. In the bowl of a food processor, combine flour, brown sugar, baking powder, baking soda, and salt, pulsing a few times to combine. Add cold butter, and pulse just until butter is mixed in. Add 1 egg and buttermilk, and pulse until dough comes together in a ball. Scrape dough out onto a well-floured work surface. Sprinkle raisins on top and a generous sprinkling of flour, and knead well until dough is not longer sticky and raisins are evenly distributed. Shape the dough into a round, place on a greased baking sheet, and slash an X on the top of the loaf. In a small bowl, beat the remaining egg, then brush the egg on the top of the loaf. Bake for 30-35 minutes, until the bread is golden.
Serve the bread sliced, warm or lightly toasted, and spread with butter and jam.
Recipe by Lulu the Baker at https://luluthebaker.com/irish-soda-bread/