Get Ready! First things first, crank your oven up to 350°F (180°C). Line a couple of baking sheets with parchment paper or those nifty silicone mats. Set 'em aside.
Dry Mix Magic: In a medium-sized bowl, whisk together the flour, baking soda, baking powder, and salt. Just a quick mingle to make sure they're all friends. Pop this aside too.
Creamy Goodness: In a large mixer bowl (stand mixer or hand mixer, your call!), beat the room temperature butter and both sugars (granulated and brown) together on medium speed. Keep going for about 2-3 minutes until it’s noticeably lighter in colour and looks wonderfully fluffy. You'll see it happen!
Egg Time: Add the egg and mix it in until it's just well combined. Don't go wild here.
Vanilla Splash: Pour in that lovely vanilla extract and give it another quick mix until combined. Smell that? Heavenly!
Bring it Together: Now, add your dry ingredient mixture to the wet ingredients. Mix on low speed until the dough is just combined. It's going to be quite thick, and it shouldn't be sticky. Super important: do not over mix! Once it’s looking mostly together, use a rubber spatula to fold it a few times and help it form a more cohesive ball.
Roll 'Em Up: Scoop out dough to create balls about 1 ½ tablespoons in size. Gently roll each one between your palms to make a smooth ball, then roll it in that extra ¼ cup of granulated sugar until it's nicely coated. Place the sugar-coated balls on your prepared baking sheets, leaving a bit of space between them as they will spread.
Bake to Perfection! Pop those beauties into the preheated oven and bake for 7-8 minutes. The cookies will spread out, and the centres will look soft but should appear "set" (not wet or doughy). You want to pull them out just before the edges start to turn golden. Seriously, don't over bake! They might look a bit puffy when they first come out, but they'll settle a bit as they cool.
Cool Down Crew: Let the cookies cool on the baking sheets for about 4-5 minutes – this helps them firm up. Then, carefully transfer them to a wire rack to cool completely before you even think about icing them (if you're using any!).