Preheat oven to 325 degrees. In a large bowl sift or whisk together flour, cocoa powder, chili powder, baking soda, and salt; set aside. Melt 4 ounces coarsely chopped Lindt chili chocolate with the butter in a small heatproof bowl set over a pan of simmering water.
Let the mixture cool slightly before proceeding.Put chocolate and butter mixture, sugar, eggs, and vanilla in the bowl of an electric mixer fitted with the paddle attachment. Turn the machine to medium speed and mix until combined. Reduce speed to low and gradually mix in flour mixture in 3 additions, do not over-mix. Fold in chocolate chunks by hand.Using a 1 ½-inch ice cream scoop, drop the dough onto parchment-lined baking sheets, spacing the cookies about 2 inches apart.
Bake the cookies about 15 minutes, or until they flatten and begin to crack.
Remove them from the oven, they should be quite soft. Lift them off the baking sheet, parchment and all, and allow then to cool on wire racks. Cookies can be stored between layers of parchment in airtight containers at room temperature up to 3 days.
