Preheat oven to 425 F and prep a baking sheet by lining with parchment paper.
Sift together flour, sugar, baking powder, and salt. Using your fingertips or two forks, cut the butter into the mixture until coarse crumbs form. Add raisins if using.
Whisk together the milk and egg. Make a well in the flour mix, and pour in the milk. Stir with a fork until a soft, moist dough has formed. Use up to 1/4 cup more milk, if necessary, adding 1 tbs at a time.
Turn dough out to a lightly floured surface and roll the dough to 1 1/2 inch thick. Slice the dough into triangles, or cut into circles with a cookie or biscuit cutter.
Transfer to the prepared baking sheet then bake until golden brown, about 14 to 17 minutes.
Serve warm with fresh Irish butter and jam.