Step 1

Preheat oven to 350 degrees. Line or grease an 8x8 pan.

Step 2

In a bowl, whisk together flour, powdered sugar, and salt.

Step 3

Mix in butter using a pastry cutter or 2 knives. Mixture should crumbly forming small pea sized clumps of dough.

Step 4

Press shortbread into pan evenly, and bake for 10-15 minutes or until the edges are beginning to brown. Remove from oven and set aside to cool slightly.

Step 5

While crust is cooling, make the filling. Whisk brown sugar, egg, and vanilla until smooth.

Step 6

Stir in flour, baking soda, and salt and mix until smooth.

Step 7

Stir in chopped walnuts.

Step 8

Pour into pan and spread evenly. Bake for 25 minutes, until the surface looks dry and the filling has set and risen slightly. Cool completely, then cut into small squares.