First off, the key to not get tough, dense biscuits is to handle the dough as little as possible. Do not use a mixer of any sort when mixing the wet and dry ingredients together, and mix just until combined. I like to use a rubber spatula and fold everything together until I can handle it with my hands. You can use a food processor to mix the dry ingredients and cut in the butter if you like, but mix in the milk and egg by hand. You will be messy, but it will be worth it :)

Preheat oven to 425°F. Prepare a cookie sheet by greasing, or covering in foil and then greasing. Rub with cold butter/shortening to lightly coat, or use cooking spray, whatever floats your boat.

Combine the milk and vinegar/lemon juice and let sit while prepping other ingredients, to give time to curdle. You can substitute real buttermilk for this instead if you like. Leave in the fridge or freezer until ready to use, as biscuits do best when all the ingredients are very cold.

In a medium sized bowl, mix together flour, baking powder, baking soda, salt, and sugar until very well combined.

Cut cold butter into slices/chunks. Add to flour mixture and cut in with pastry cutter or 2 butter knives, or use hands to mesh together until mixture resembles small peas.

*Note: I like to cut in half of butter to a course meal texture, then cut in the other half to look like small peas. The bigger your butter chunks, the more flaky your biscuits will be, but some smaller pieces mixed in makes them moist. If using hands, chill mixture for 15 minutes afterwards, as your hands will warm everything up slightly.

Take out your milk and vinegar/lemon juice mixture from the fridge/freezer. Stir the egg into the milk mixture (or dump in separate bowl and mix) until incorporated, no need to thoroughly beat. (This makes it easier to combine all ingredients without over-mixing.)

Make a well in the center of the dry ingredients (flour mixture and butter). Add the milk and egg mixture and GENTLY combine, folding or lightly stirring with a fork or rubber spatula.

Add the last 1/4 c of milk/water as needed, 1 T at a time, until mixture comes together. Dough will be wet and slightly sticky, but should not be overly sticky or gluey.

You now have 2 options. You can cut biscuits, or do drop biscuits. If doing drop biscuits, just drop large spoonfuls of dough onto prepared cookie sheet, then bake 12-15 minutes until edges are browning and cooked all the way through. If cutting, move on to next step.

Lightly flour (tastes amazing if using a mixture of flour and powdered sugar, still doesn't taste too sweet) a baking mat or your counter top, and dump the dough on top. Optional: gently knead 3-4 times, NO MORE, to make dough somewhat layered. Then let rest for 5 minutes. You can just dump and flatten the dough, without kneading, which may be the best option if you feel you may have worked the dough a little too much.

Press with hands (no rolling pin, makes it tough) into a rectangle, at least 1 inch to 1.5 inches thick. Thick=tall, soft biscuits, thin= flat, hard biscuits. You can lightly dust flour on top of the dough, then use plastic wrap on top of the dough to press to a rectangle, to keeps hands cleaner.

Cut biscuits. Use something very sharp, and do not twist while cutting. I prefer to use a large, sharp knife to cut my rectangle into 12 squares, so I do not have to re-form and cut dough again. If you want round biscuits, use a biscuit/cookie cutter that is SHARP. A glass or jar lid is too blunt and will seal the edges, not allowing steam to escape, therefore the biscuits will not rise much. If making round, cut out as many biscuits as you can and re-form the dough scraps to cut more out. Do not do this more than twice, they will get tough. Seriously, square is just as cute and is faster :)

Place cut-out biscuits on prepared cookie sheet. Leave them touching if you want fluffier biscuits with soft edges, spread out if you want crispier, browner edges and slightly flatter biscuits. Bake 12-15 minutes, until just starting to brown on top (golden brown is typically too done, unless you brushed the tops with melted butter before cooking) and done all the way through. You may have to adjust the cooking time slightly depending on your oven, altitude, thickness of the dough, etc.

Now enjoy your hard work! Best when fresh from the oven, but still pretty good reheated the next day. If you only want to make a few at a time, you can freeze a cookie sheet full of uncooked biscuits until the dough is frozen solid, then put in a baggie and keep in the freezer for a couple months. When you want some, bake desired amount at 425°F for a few extra minutes, I'm guessing 15-17 but keep checking them!