Preheat the oven to 350ºF (180ºC). Line two large cookie sheets with parchment paper.
In a large bowl, whisk together the flour, cocoa powder, baking soda and salt.
In a separate large bowl, cream the butter, granulated sugar and brown sugar together with an electric mixer at medium speed, until light and fluffy.
Beat in the eggs and vanilla in three separate additions, making sure each addition is incorporated before adding the next. Beat in the flour mixture just until combined.
Set aside 20 chunks of the chopped chocolate. Fold the remaining chopped chocolate, the caramel chips and the toffee bits into the dough.
Place twenty 2-inch size portions of dough about 2-inches apart onto the prepared cookie sheets. (I used a #24 portion scoop*)
Top each cookie with a chunk of the reserved chocolate and a pecan half. Bake until the surface of the cookies is set, about 10-11 minutes. Let cool on the baking sheet for 1 minute then transfer to a cooling rack.