Christmas Butter "Spiral" Cookies

Cut the cold butter into cubes and place it in a food processor with the powdered sugar, salt, vanilla and part of the flour. Blend until it forms buttery crumbs. (A small chopper works but you may need to work in batches; a large food processor holds the whole amount. The dough can also be made by hand like any butter dough - just work quickly so the butter does not soften too much.) Add the egg to the buttery crumbs and blend for about 30 seconds until the egg is incorporated. Tip out onto the work surface and add the remaining flour, working until you have a smooth dough. If it becomes too firm, you can add 1 tablespoon of cold water. Divide the dough into two halves and color one half with red food coloring. Wrap both halves in plastic wrap and refrigerate for 1 hour until firm. On a floured surface, roll out two rectangles and lay one on top of the other. Trim the edges (save the trimmings for later). Roll the two colors up into a tight log, then roll the log in sugar pearls, pressing lightly so they stick well to the outside. Wrap the whole log in plastic wrap again and chill for 30-40 minutes so it is well cooled and the cookies slice easily. Slice the firm log into cookies less than a centimeter thick (about 0.5-0.7 cm) - not too thick. Mix and press the dough trimmings together randomly to create a marbled effect (it also works well with cocoa). Wrap this trimmings log in plastic and chill as well. Bake the cookies in a preheated 180°C oven for 10-12 minutes. When they come out of the oven they are still soft; leave them on the tray for 4-5 minutes and they will firm up on their own.