Preheat the oven to 180 C/350 F. Line a large baking sheet with parchment paper.: You will notice the warm dry scent of the oven as it comes up to temperature, and the parchment creates a matte, nonstick surface so the cookies brown evenly. Proper preheating ensures consistent rise and spread; an oven that is not fully hot will make cookies spread too thin. A common pitfall is placing cold dough into an underheated oven which can produce flat, greasy edges.
In a mixing bowl, add the pecan butter, egg, brown sugar, and baking soda, and mix well. Fold through the pecan and chocolate chips.: At this stage you should smell the nutty aroma of the pecan butter blending with the caramel notes of the brown sugar . The mixture should look glossy and cohesive, not dry or crumbly. Folding in the chopped pecans and chocolate chips last preserves their texture and keeps chocolate from melting into the batter. Overmixing here will break down the bits and can make the final cookie tough, so mix just until combined.
Cover the bowl and refrigerate the cookie dough for 30 minutes.: Chilling lets the dough firm up so cookies spread less, creating a thicker center and crisp edge contrast. You may detect the scent of sugar mellowing as the fats solidify. If you skip chilling, expect thinner cookies; the dough may also be harder to portion. Do not leave the dough in the fridge for days without checking for freshness, especially if your kitchen is warm.
Scoop out 12 portions of cookie dough and place them on the lined sheet. Press down on each ball of cookie dough into a cookie shape.: The dough should be cool and slightly tacky, not sticky. When you press them, you'll hear a faint soft thud and see the tops flatten a touch; this helps them bake evenly with an appealing shape. If the dough is too warm and spreads too much, pop the tray back in the fridge for a few minutes. A frequent mistake is making portions uneven which leads to inconsistent bake times.
Bake the cookies for 10-12 minutes, or until the edges are mostly firm.: As they bake you will notice the aroma deepen, with the pecans toasting and the chocolate chips softening. The visual cue to watch for is lightly golden edges while the centers still look slightly soft, because they will continue to set off heat. Overbaking makes them dry, so pull them out when edges are set but centers are not completely firm.
Remove the cookies from the oven and let them cool completely.: Cooling lets residual heat finish the bake and the cookies will firm up to the ideal texture. You will feel a textural change when they shift from soft to pleasantly chewy. If you try to move them while too warm they may deform, so give them time to cool on the sheet for a few minutes before transferring to a rack. A common error is stacking warm cookies which traps steam and makes them soggy.