This recipe can be easily doubled if desired. I will often double it, and then divide the dough into four equal portions and make the different shortbread cookie variations (which you can find elsewhere on this site) for a nice variety for the holidays. —Food52
Pre-heat oven to 350 F degrees. Line a baking sheet with parchment paper. In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and powdered sugar until pale and fluffy – about 5 minutes.
Scrape down the sides of your bowl and add in the vanilla; Beat until combined.
In a small bowl, whisk together all purpose flour, rice flour and salt. Add the dry ingredients (including chopped pecans and toffee bits) to the wet in two additions, beating on medium until combined and the dough begins to pull away from the sides of the bowl.
Divide the dough into two parts and press into two 8 inch fluted edge tart pans with a removable bottoms.
Bake at 350F for 25-30 minutes or until the tops are a light golden brown. Remove from the oven and allow to cool completely.
Once cooled, remove the bottom of the pan and slice the shortbreads into slices like you would a pie. Dip the fluted edge into melted dark chocolate and place on a sheet of parchment paper to set. While the chocolate is still warm, sprinkle with more chopped pecans if desired.
Allow the chocolate to set for thirty minutes at room temperature before serving or place the slices in the fridge for a few minutes to speed up the process.