In the bowl of a stand mixer, use a whip to beat together butter, powdered sugar and salt.
When they are combined, add the vanilla and cream. Beat until no lumps remain.
Melt chocolate carefully in the microwave (checking every 30 seconds) or by another method if you prefer.
Beat chocolate into the butter mixture. Stir in nuts until combined.
Press into a 9x9 pan. cut into 16 squares and serve.