Preheat your oven to 350°F (175°C).
In a medium saucepan over low heat, melt the butter and semisweet chocolate chips together, stirring constantly until smooth. Remove from heat and let it cool slightly.
Once the chocolate mixture has cooled slightly, stir in the sweetened condensed milk and vanilla extract until fully combined.
In a separate bowl, whisk together the all-purpose flour. Gradually add this mixture to the chocolate mixture, stirring until just combined.
Fold in the chopped pecans until evenly distributed throughout the cookie dough.
Using a tablespoon or cookie scoop, drop spoonfuls of the dough onto your prepared baking sheet, leaving some space between each cookie. Bake for about 7 minutes or until the edges are set but the centers are still soft.
Remove from the oven and let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
