Preheat your oven to 350°F or 180°C. Line your baking sheet with parchment paper. This prevents sticking. Always prepare your tray before mixing the dough. It saves time later.

In a large bowl, beat softened butter, brown sugar and white sugar together. Mix until light and fluffy. This step adds air to the dough. It helps create soft and chewy cookies.

Add the egg and vanilla extract to the bowl. Mix until smooth. Scrape down the sides if needed. The mixture should look creamy and well combined before adding dry ingredients.

In another bowl, combine flour, baking soda and salt. Stir gently to mix evenly. Slowly add the dry mixture to the wet mixture. Mix until just combined. Do not overmix the dough.

Scoop small balls of dough onto the baking sheet. Leave space between them. Use your thumb to press a small dent in the center of each cookie. This space will hold the filling.

In a small saucepan, combine corn syrup, brown sugar and butter. Heat gently until smooth. Stir in chopped pecans and vanilla. Let it cool slightly. The mixture should be thick but spoonable.

Spoon a small amount of pecan filling into each cookie dent. Do not overfill. Bake for about 12 to 15 minutes. The edges should look golden. Let cookies cool before moving them.