Position the racks in the middle and lower third of the oven. Preheat the oven to 350 degrees Fahrenheit. Line 3 large cookie sheets with parchment paper.

Into a small bowl, sift together the flour, baking soda, and salt.

In the bowl of a standing electric mixer, cream the butter with both sugars on medium speed until light and fluffy. Add the whole egg, egg yolk, and vanilla and beat until blended. Add the dry ingredients, 1 cup at a time, beating after each addition, but don't overbeat. By hand, stir in the pecans and chopped chocolate, mixing until evenly distributed.

Using a small cookie scoop or a teaspoon, spoon the dough onto the lined cookie sheets, leaving about 1 ½ inches between the mounds. With your fingers, flatten each cookie ½ inch thick.

Bake the cookies for 15 to 18 minutes, rotating the cookie sheets between the racks halfway through baking and turning them front to back as well, until the edges of the cookies start to turn golden brown. Cool the cookies on the sheets, set on racks. Store in an airtight container.