Preheat oven to 375° F. Place flour, brown sugar, baking powder, baking soda and salt in a large mixing bowl. Whisk the dry ingredients together. Use a pastry blender (or two forks), to cut in very cold butter, until the mixture is crumbly, and the butter is about the size of peas.
In a separate container, mix together buttermilk and one egg, and pour it into the bowl with the dry ingredients. Stir to combine, but only until flour mixture is just moistened. Do not overmix! The batter will be fairly sticky/tacky. Add the raisins, and fold them into the dough.
Transfer the dough onto a floured work surface. Lightly sprinkle with additional flour, and knead dough for 1 minute, adding flour as necessary. Shape the dough into a round loaf. Place the loaf onto a well greased baking pan/sheet. Use a sharp knife, and cut a cross shape in the top of the loaf, cutting about 1/4" deep.
Lightly beat the one remaining egg, and brush it over the top of loaf. Bake for 30-35 minutes in a preheated 375° F. oven. When done, the bread should be golden brown and "set" in the top/middle of the loaf. Transfer the loaf to a wire rack to cool for a few minutes before slicing. Slice loaf into 8 slices, spread with softened butter, serve and enjoy!
Irish Soda Bread https://www.thegratefulgirlcooks.com/irish-soda-bread/