Preheat oven to 375°.
Mix together flour, baking soda, baking powder, and salt. Set aside.
Beat butter on medium-high speed until creamy, about 1 & 1/2 to 2 minutes. Add dark brown sugar and beat for 2-3 minutes. Add granulated sugar and beat for another 2-3 minutes. Add eggs one at a time, mixing well after each. Add vanilla and beat for about 30 seconds.
Gradually add dry ingredients. Stir in chocolates.
Drop dough by tablespoonfuls onto baking sheets (ungreased or with Silpats) about 3 inches apart. Do not crowd cookies because they will spread. Place two or three pecans on top of each mound of cookie dough.
Bake for 8-10 minutes, or until tops are just set and the edges are lightly browned.
Cool cookies for 4-5 minutes, then transfer to wire racks to cool completely.
Makes about 4 dozen cookies.
*Use any combination of chocolates you like. The original recipe lists white, semi-sweet, and milk chocolates.