Updated Nov 15, 2019Chatelaine
1. Position rack in centre of oven, then preheat to 325F. Line 2 baking sheets with parchment.
2. Sift flour with cornstarch and salt in a medium bowl. Beat butter with sugar in a large bowl, using an electric mixer on medium-high, until very pale and fluffy, 4 to 5 min. Add milk, zest and vanilla and beat for 1 min.
3. Reduce speed to low and beat in flour until just combined. Stir in cranberries. Spoon half of batter into a piping bag fitted with a large, open star tip. Squeeze bag and pipe batter into an ‘S’ shape (about 2 in. long and 1 in. wide), 1 in. apart, on a prepared sheet. (Cookies will spread as they bake.)
4. Bake until edges are dark golden, 15 to 17 min. Let stand on sheet for 3 min, then transfer to a rack to cool completely. Repeat with remaining dough.
For the large, open star piping tip, we used Ateco #8.
Cookies will keep well stored in an airtight container up to 5 days.