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Whisk together the flour and salt and then sift this into another bowl. Cover and set aside. When the butter has become very soft (just shy of being oily) on medium speed, cream the butter 1 cup of sugar until homogenous without beating in too much air. Mix in the vanilla. Add the flour mixture and combine. Once the mixture has come together, remove the bowl from the machine and, using your working hand, reach down to the bottom of the bowl and bring the dough up from the bottom, working things together until the dough is cohesive throughout.
Dump one half of the dough a long, doubled sheet of plastic wrap. Cover the dough with the plastic and use your hands to pull the dough into a log 1 ½ to 2-inches thick. When satisfied with the shape of the log (it should be uniform in girth) rap wrap again in foil. Chill the dough for 30 minutes (or longer) or freeze. (To thaw, leave in the fridge overnight). If the dough chills for much longer than 30 minutes, allow it to soften just a bit at room temperature (which will make is less likely to crumble when you slice the log into rounds).
Preheat the oven to 350ºF. Line two cookie sheets with parchment paper. Working with one log at a time, unwrap the chilled dough and slice into ½ inch thick rounds. (If you see that the log had formed a flat edge from being chilled on one side, roll it on your work surface to help round out the log.) Place the rounds on the prepared baking sheets (you will have 4 rows of 4 cookies on each sheet, plus one or two more, depending on girth of your logs and the depth of your slices) Sprinkle (or roll each round) evenly with more sugar and bake at 350ºF until light golden brown, 18 to 23 minutes (baking time will depend on the temperature of the dough when being cut). (If using the convection oven, check at 18 minutes).
Allow cookies to cool on their sheets, on wire racks, placed over sheets of wax paper. Once cool, if desired, either drizzle or dip half of each cookie with melted chocolate (if not tempering the chocolate, use melting wafers which don’t need tempering). Place directly on wax paper to allow chocolate to set.
Whisk together the flour, cocoa powder, powdered sugar and salt. Sift this into another bowl. Cream the butter with the sugar until combined, mix in the vanilla. Add the flour/cocoa mixture and mix until homogenous (check for any dry pockets on the bottom of the bowl).
Form logs as previously described and chill until firm enough to slice. Slice the log into rounds, place on parchment lined baking sheets and, if possible, cover and chill the unbaked cookies. (This helps to maintain their shape since this dough is a bit softer than the other version).
Preheat the oven to between 325ºF and 350ºF. Sprinkle the unbaked cookies with sugar and bake for about 25 minutes, or until the dough seems to be turning golden around the edges. (Determining the color of these cookies is not as easy since the dough is dark.) The tops should feel set on top. Cool and apply chocolate as previously described.
Once cool (and chocolate is set, if using) store cookies in an airtight tin, at room temperature.