Beat 1/3 cup pure maple syrup, 2 egg yolks and ½ tsp vanilla extract in a large bowl with an electric mixer on medium-high until thickened, about 1 minutes. Add 2 tbsp flour and beat until combined. In a separate bowl, beat 2 egg whites and 1/8 tsp salt on high until stiff peaks form, 1 – 2 minutes. Fold into yolk mixture. Pour into 4 lightly greased 5 oz ramekins set on a rimmed baking sheet. Place in lower third of a 400 degree oven and immediately reduce temperature to 375 degrees. Bake until puffed, 12-14 minutes. Dust with powdered sugar. Serves 4.