Combine the flour, cocoa, baking soda, and salt in a medium bowl. Mix thoroughly with a whisk and set aside. Combine the sugars in a small bowl and mix well with your fingers pressing out any lumps. (Combine in a food processor if lumps are stubborn.)
In a medium mixing bowl, using a hand mixer, beat the butter and margarine until creamy. Add sugar mixture, cinnamon, peppers, and vanilla. Beat on high speed for about 1 minute. Beat in the egg white and until the mixture is smooth. Stop the mixer. Add the flour mixture, beating on the lowest speed, just until incorporated. Gather the dough together with your hands and form it into a neat log, 9 to 10 inches long by 1 1/2 inches in diameter. Wrap in waxed paper or plastic wrap. Fold or twist ends of the paper without pinching or flatting the log. Refrigerate at least 45 minutes, or until needed.
Put the oven racks in the upper and lower third of the oven and preheat to 350 degrees F. Line baking sheets with parchment paper or aluminum foil.
Use a sharp knife to slice rounds of chilled dough, a scant 1/4-inch thick. Arrange the cookies, 1-inch apart, on the prepared baking sheets. Bake 12 to 14 minutes. Rotate the baking sheets from top to bottom and front to back about halfway through. Cookies will puff and crackle on top, and then begin to settle down slightly when done.
Remove the baking sheets from the oven and use a metal spatula to transfer the cookies to a wire rack to cool. Allow the cookies to cool completely before storing or stacking. Store in an airtight container up to 2 weeks, or freeze up to 2 months.
To spice things up, after the cookies are baked, let them cool on a wire rack, drizzle with dulce de leche and sprinkle chopped almonds on top.