In a medium bowl, whisk together the flour, baking soda and salt and set aside. In a small saucepan or microwave, melt the butter. Stir in both sugars and whisk until smooth. Add the egg yolks and vanilla and whisk again. Pour the butter mixture into the flour mixture and stir until just combined. While the mixture is still warm, fold in half a cup of the chocolate and stir. Let the mixture cool a bit and then add the remaining chocolate and pecans. The dough will be very loose. Cover the bowl with plastic wrap and chill until the dough is firm, several hours or overnight.