Preheat the oven to 350°F (convection) and line a baking sheet with parchment paper.

In a stand mixer fitted with a whisk or paddle attachment, beat the room-temperature butter and brown sugar for 1–2 minutes, until light and off-white.

Mix in the vanilla extract and egg yolk until fully combined.

Add the all-purpose flour and baking powder, then gently fold in the chocolate chips or chunks just until incorporated.

Scoop 1-teaspoon portions of dough and place on the prepared baking sheet.

Bake for 7–8 minutes, until the edges are set and the centers remain soft.

For perfectly round cookies, immediately swirl a round bowl, cup, or cookie cutter around each cookie while warm to clean up the edges.

Let cookies rest on the baking sheet for about 10 minutes before transferring.

Finish with flaky sea salt, if desired.

Enjoy fresh, or store in a chilled environment for up to 8 days.