Preheat your oven to 400 F or 200FAN.
Prepare your dough by combining all of the dry ingredients (flour, sugar, salt, baking powder and baking soda) into a mixing bowl and whisk to combine.
Add the grated butter to the dry ingredients and combine it with your fingers until the consistency is that of large breadcrumbs.
Beat together the egg and the milk.
Add the egg/milk mixture to the dough and mix it with your hands until the dough has just come together.
Flour your work surface and turn the dough out.
Pat the dough (gently) into a rectangle-ish shape and then fold the dough. I fold it in half, then pat it down, then fold it in half in the other direction, and repeat until the dough has completely come together and no longer has any large cracks. Roll the dough to about 1/2 - 3/4 inch thick. The dough will seem thin, but since these are standard, baking powder biscuits made with AP flour (not self-rising flour) they'll puff up nicely when they hit the heat. If we were making shortcake for example, we'd roll out a thicker dough, but for now, a thinner dough is just fine.
Cut your biscuits. You can use whatever you have to do this! A biscuit cutter is ideal, but a drinking glass works fine, too! If you want to, re-roll the scraps and make additional biscuits. Note: I prefer smaller biscuits, so I cut mine fairly bite-sized, but these can be cut as large or as small as you like. If you don't want round biscuits, you can always cut squares. As long as you stick with a thinner dough, you're good to go!
Place the cut biscuits on a parchment-lined baking sheet and pop them into the preheated oven. Bake them until they're golden and crispy on top, about 12-15. minutes. Serve hot!