Meanwhile, place a piece of parchment or waxed paper on baking sheet. Draw 11/2 to 2-inch (3.5 to 5 cm) tree outlines or trace around 2-inch (5 cm) tree-shaped cookie cutter, leaving 1/2-inch (1 cm) space between each tree. Centre toothpick at bottom of and 1/2 -inch (1 cm) into each tree outline. In small saucepan, heat chocolate chips and the shortening over low heat, stirring constantly, until chips are melted. Pour chocolate into decorating bag fitted with plain tip or resealable plastic bag; snip one corner. Starting at top of each tree outline, pipe chocolate over tree and end of toothpick within tree; fill centre with random, squiggly lines. Refrigerate until chocolate hardens. Gently remove trees from paper; refrigerate until serving.