Preheat the oven to 350°F. Lightly grease an 8" square pan., For the blondies: In a medium bowl whisk together the flour, salt, and baking powder and set aside., In a medium heatproof bowl in the microwave, or a 2-quart saucepan, melt the butter and brown sugar together. Remove from the heat and stir in the syrup., Let cool to lukewarm, then stir in the eggs, one at a time. Add the maple flavor., Stir the dry ingredients into the butter mixture until evenly combined. Stir in the nuts., Transfer the batter to the prepared pan and bake for 25 minutes, until the top is shiny and the edges just begin to pull away from the pan. Remove from the oven and let cool before cutting., For the glaze: Whisk together all the ingredients, adding more liquid as needed to get a pourable consistency. Drizzle over the cooled bars., Store at room temperature for 5 days, or freeze for up to 3 months., Yield: sixteen 2" squares.