1. In medium bowl, combine flour and granulated sugar.
2. Using pastry blender, or by hand, cut in butter.
3. Press into 13 x 9 inch cake pan.
4. Bake in 350F oven for 20 to 25 minutes until set.
5. Set aside on cooling rack.
1. In medium bowl, whisk together eggs and brown sugar.
2. Add butter, vinegar and vanilla. Stir well to combine.
3. Stir in pecans.
4. Pour mixture over baked shortbread crust.
5. Tent edges with foil to prevent over-browning.
6. Bake for 20 to 25 minutes. Topping will be slightly firm when touched and the centre will still be a little jiggly.
7. Cool in pan on baking rack.
8. Cool squares at least 2 hours before cutting.
9. Lift squares with a metal spatula or knife.
Store in refrigerator for up to one week. Allow to come to room temperature before serving.
Squares may be frozen for up to 3 months. Layer on waxed paper in plastic container.