Preheat oven to 350 degrees.
Spray a 9X13 glass casserole dish with bakers spray. Set aside.
In a medium sized bowl, combine the flour, pumpkin pie spice and kosher salt. Set aside.
Using a hand mixer, cream the butter and sugar for a few minutes until creamy.
Add the eggs one at a time, beating with each addition.
Add in the vanilla butter nut flavor and stir.
Gently incorporate the flour mixture into the wet mixture and stir until just combined. Do not over mix.
Fold in the grated sweet potato and walnuts.
Place batter into baking dish and spread evenly.
Bake for 30-35 minutes or until toothpick come out clean.
Icing - Combine cheese and butter with a mixer until smooth.
Add sugar and mix until combined.
Stir in vanilla and mix.
Spread on cooled brownies. Garnish with more walnuts. Cut into 20 squares. Say Grace and enjoy!!