Combine 1 3/4 cups flour with the cornstarch and whisk until combined.
Add the butter and sugar to the flour mixture and beat at medium speed, scraping bowl often, until mixture resembles coarse crumbs. Stir in 1/3 cup finely chopped pecans.
In a 9X13 baking pan press the crust mixture into the bottom evenly.
Bake 18-22 minutes or until edges are very light golden brown.
Filling
In a large bowl add the brown sugar, 6 tablespoons flour and salt and whisk until combined.
Add in the corn syrup, eggs and vanilla; mix well. Stir in 1 1/2 cups chopped pecans.
Spread evenly over hot, pre baked crust.
Bake 30-35 minutes or until filling is set and a knife inserted 1 inch from edge comes out clean.
Cool completely on the counter then refrigerate 30 minutes. Cut into bars and serve.