Preheat the oven to 375°F. Grease the bottom and sides of the pan with the extra butter. Set aside.
Whisk the flour, salt, and baking soda in a large bowl.
Grate cold butter into the flour mixture, stirring occasionally to prevent clumping. Alternatively, you can use a pastry cutter or blender in the place of a grater. Stir to distribute the butter throughout the flour.
Make a well in the center of the dry ingredients. Add the buttermilk and egg. Stir just until the dry ingredients are moistened. If the mixture is too dry, add a little extra buttermilk.
Turn out the dough onto a lightly floured surface. Use your hands to form a round mound and place it into the prepared pan.
Use a knife to cut a deep X into the top of the bread.
Bake for 35 minutes or until the bread is lightly browned on top and an inserted toothpick or tester comes out clean. Remove from the pan and then cool on a wire rack. Brush melted butter across the top if desired.
Notes
Baking Soda
Baking soda begins to lose potency after about six months once the box is opened, while an unopened container lasts up to three years. To check if your baking soda is still effective, perform a simple test: add 1/4 teaspoon to 2 teaspoons of vinegar. If it foams vigorously, it’s still good to use; if the reaction is weak or nonexistent, it’s time to replace it. For this recipe, use only fresh baking soda for the best results.
Buttermilk
Shake the buttermilk because it can separate while sitting.
Add-Ins
Here are ideas for Irish soda bread add-ins.
Dried Fruit
Add 1/2 cup of dried fruit such as raisins, cherries, cranberries, or blueberries to enhance this bread's taste. Add 2 tablespoons of sugar to sweeten the bread.
Herbs
Add two tablespoons of fresh herbs, such as rosemary, to the dry ingredients and whisk. Other delicious herbs in this bread include thyme, basil, and fennel. If using dried herbs, add 1 tablespoon instead.
Cheese
Add 4 ounces (about 1 cup) of grated cheese, such as cheddar, to this bread.
Onions
Finely chop and saute a large onion in olive oil. Add the cooked onions to the flour mixture just before adding the buttermilk.
Seeds
Caraway and fennel seeds are delicious in this bread. Add 2 teaspoons of your chosen seed to the dry ingredients and whisk.
Oatmeal
Add 2 tablespoons oatmeal to the flour mixture and whisk.