To toast the barley flour, warm a large pan over medium heat. Add 2 cups of barley flour and stir frequently until the flour starts to brown and take on a nutty smell, approximately 5-7 minutes. Remove pan from the heat and allow the flour to cool. Add flour through a sieve to remove any clumps that may have formed. Reserve flour.
Tip: toast 2 cups rather than the 1 1/2 cups called for in the recipe as the flour has a tendency to form clumps during the toasting process.
Pre-heat the oven to 350 F. In a mixing bowl, cream the butter, sugars (brown and powdered) and vanilla together. Add the flour, cream and salt and stir gently until just combined. If the dough will not come together to form a loose ball, add a teaspoon of water at a time until it does.
Place the crumbly dough on a sheet of parchment and roll in the paper to form a 12-inch log. Sprinkle liberally, covering all sides of the dough with the turbinado sugar. Roll the log again in the parch-ment to press in all the sugar, then wrap the dough tightly with plastic wrap. Refrigerate for at least 1 hour or until chilled through.
Remove the log from the refrigerator and slice into ¼-inch pieces and bake on a parchment-lined baking sheet for 12-15 minutes. Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Use this recipe for a shortbread base for cheesecakes, as the crust for pies filled with custard and topped with fruit or replace portions of the flour in bread and cookie recipes with toasted barley flour.