Start by preheating your oven to 180°C (350°F). Line one or two baking sheets with parchment paper or silicone baking mats to prevent sticking and promote even baking. Set these aside while you prepare the dough. This is also a good time to bring your butter and egg to room temperature, if you haven’t already-this helps everything mix together smoothly.

Use the spoon-and-level method for measuring flour. First, fluff up the flour in the container. Then gently spoon it into your measuring cup until it overflows. Level it off with the back of a straight dinner knife (not serrated). Add the measured flour to a bowl, then whisk in the baking soda and optional baking powder. Set the dry mix aside.

In a large bowl, use a hand or stand mixer to cream the room-temperature butter and 1½ cups of sugar. Beat on medium speed until the mixture looks light, pale, and fluffy-about 2 to 3 minutes. This step gives the cookies their soft texture and buttery flavor.

Crack the egg into the butter-sugar mixture and beat on low until fully incorporated. Make sure to scrape down the sides of the bowl so everything blends evenly. The dough will start to come together and look smooth and slightly glossy.

With the mixer on low, slowly add the dry flour mixture to the wet ingredients in batches. Mix just until all the flour is incorporated and a soft dough forms-do not overmix. Use a cookie scoop or spoon to portion the dough into 1-tablespoon-sized balls. Roll each ball in extra white sugar to coat it lightly.

Place the sugar-coated dough balls onto your prepared baking sheets, leaving about 2 inches between each one to allow for spreading. Bake for 10–12 minutes, or until the edges are set and the bottoms turn a light golden brown. Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to finish cooling. Serve once fully cooled.