Make the buttermilk substitute by combining dairy free milk (for a vegan version) or milk (as a buttermilk swap) with the freshly squeezed lemon juice or vinegar. Let it sit for 10 minutes to "curdle" and thicken.

Heat the oven to 400 F and make sure the oven rack is in the center position. Prepare a baking sheet by covering it with parchment paper. You can also grease or use parchment on the bottom of a 8-10" cast iron skillet, a cake pan, or use a 5-quart round Dutch oven (without the lid).

In a large mixing bowl combine both flours, salt, baking soda, and sugar until it's well combined.

Add in the cold butter cubes by cutting it in with a pastry cutter or a fork until it resembles pea-sized pieces.

Pour the buttermilk substitute into the flour mixture all at once and stir it with a fork until the liquid is absorbed and the bread dough starts to hold together like a rough biscuit dough. The dough will be wet but if it's too sticky, mix in a tiny bit more flour. Stir in the raisins if you're using them.

Flour a cutting board and transfer the dough to a cutting board. Using your hands, form the dough into a round dome shape loaf that's about 8-9" in diameter. Transfer the dough to the prepared baking sheet or pan.

With a sharp knife, make a deep ¾" X shape into the loaf.

Bake the Irish soda bread for 45-50 minutes or until the bread is golden brown and a cake tester or wooden skewer comes out clean. If the bread seems to be browning too fast during cooking, you can add foil over the top.

Remove the bread from the oven and let it cool on a wire rack. Serve warm or cold with a butter substitute or jam. Enjoy!