1-First Step: Make the pecan pie filling Start by whisking the brown sugar, heavy whipping cream, egg, vanilla extract, corn syrup or maple syrup, and salt in a small bowl until smooth. Stir in the coarsely chopped pecans, then pour the mixture into a small saucepan. Cook over medium heat while whisking constantly until it just begins bubbling and thickens slightly. Do not overcook it, or the egg can curdle.

2-Second Step: Cool and chill the filling Once the filling thickens, remove it from the heat and let it cool. Then refrigerate it for about 1 hour. This step matters because the filling needs to be firm enough to spoon into the cookie centers without running everywhere. A well-chilled filling also helps the cookies hold their shape better during baking.

3-Third Step: Mix the cookie dough In a large bowl, cream the softened butter, granulated sugar, and packed light brown sugar until fluffy. Mix in the egg yolk, vanilla extract, and whole milk. In another bowl, whisk or sift together the flour, baking soda, baking powder, and salt. Add the dry ingredients to the wet ingredients and mix just until a smooth dough forms. Overmixing can make the cookies tough.

4-Fourth Step: Chill the dough Cover the dough and chill it before shaping. This helps the flour hydrate and keeps the cookies from spreading too much. It also makes the dough easier to portion, which matters because this recipe works best when you make exactly 13 cookies. That gives you the right dough-to-filling ratio.

5-Fifth Step: Shape and fill the cookies Portion the chilled dough into 13 balls and place them on prepared baking sheets. Use your thumb or the back of a spoon to make a deep indent in the center of each ball. Spoon the chilled pecan filling into each indent, filling them generously but not so much that the filling spills over.

6-Sixth Step: Chill again before baking Once filled, refrigerate the cookies again before baking. This extra chill helps them stay thick and gives you a cleaner shape in the oven. It also helps create that lovely contrast between the buttery cookie edge and the gooey center.

7-Seventh Step: Bake until golden Bake the cookies at 375°F (190°C) for 8 to 12 minutes, just until the edges are golden and the centers look set but still soft. Avoid underbaking, because the filling needs enough heat to finish setting. At the same time, do not overbake, or the cookies may dry out.

8-Eighth Step: Cool and finish Let the cookies cool on the baking trays before moving them. This keeps them from falling apart while the filling is still soft. Once cooled, top them with the remaining pecan filling, chopped pecans, and a drizzle of melted dark chocolate if you like. Then serve and enjoy while they are still slightly warm or fully cooled.