In a large mixing bowl, combine the softened butter and sugar. Beat on medium speed for 3 minutes until the mixture is light, fluffy, and pale—this incorporates air into the dough, which helps the cookies rise and gives them a tender crumb. I like using Kerrygold butter because its higher fat content creates a richer, more flavorful cookie that stays soft longer.

With the mixer still running on medium speed, add the room-temperature egg first, beating for about 1 minute until fully incorporated. Then add the vanilla and mix for another 30 seconds. The room-temperature egg emulsifies more smoothly into the butter-sugar base, creating a better texture. Next, add the Greek yogurt in a few additions, stirring gently between each addition until just combined—the yogurt will thin the dough slightly and add a subtle tang that enhances the cookie flavor.

In a separate small bowl, whisk together the flour, baking powder, baking soda, and salt—this distributes the leavening agents evenly throughout the dough and prevents lumps. Add the dry ingredient mixture to the wet mixture in the bowl and fold gently with a spatula until just combined. Don't overmix; a few flour streaks are fine. Overmixing develops gluten and can make cookies tough, so I always stop as soon I see no dry flour.

Transfer the dough to a piece of plastic wrap or parchment paper, wrap it tightly, and refrigerate for at least 4 hours (or overnight). Cold dough is easier to work with, spreads less during baking, and allows flavors to develop. This step is non-negotiable for the best texture and shape retention.

Remove the chilled dough from the refrigerator and let it sit at room temperature for 5 minutes for easier handling. On a lightly floured surface, roll the dough to about 1/2-inch thickness. Cut into desired shapes using cookie cutters and place each cookie about 2 inches apart on parchment-lined baking sheets. The spacing ensures even baking and allows for slight spreading.

Preheat your oven to 350°F and bake the cookies for 10-11 minutes, until the edges are set but the centers still look slightly soft—they'll firm up as they cool. The cookies should be pale blonde, not golden brown. Remove from the oven and let them cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely before frosting.

While cookies cool, beat the softened butter with vanilla, salt, and 1 tablespoon of cream on medium speed for 1 minute until smooth. Gradually add the sifted powdered sugar, beating on low speed to avoid a sugar cloud, then increase to medium speed and beat until light and fluffy, about 2-3 minutes. Add the remaining tablespoon of cream (or more as needed) to reach your desired spreading consistency. Once cookies are completely cool, spread or pipe frosting onto each one and immediately top with sprinkles while the frosting is still soft.