until golden brown, about 20 minutes; turn cookies over once while baking. Cool on reacks. If made ahead, package airtight up until next day or freeze. To build the tree, pipe (using a 1 cm tip) or spread a little frosting on 1 side of each of the longest cookies. Lay icing-side down on a flat platter, tips touching, to form a triangle. Pip or spread icing down center of each cookie on plate. Stack the 3 next-longest cookies on the first, inverting position of the triangle (looking down from the top, it will look like a Star of David). Build tree, using the next-smallest cookie trio for each level and cementing with icing. If you like, pipe icing to drip over the edge of the cookies. Decorate top with holly. Let guests lift off cookies to eat. If made ahead or to protect from dust, seal in plastic wrap; cookies stay fresh up to 4 days, depending on moisture in air. Kept longer, they hold their shape but get stale. Icing: Smoothly mix together 0.75 cp orange marmalade, 1 box (1 lb) or 4 cups sifted powder and 1 Tablespoon orange-flavor liqueur or orange juice. If icing thickens as you work, stir in a little more orange juice.