Sweet Rhubarb Snack Bars

Ingredients

• 2-1/4 cups unbleached all-purpose King Arthur flour
• 1 cup King Arthur stone ground white whole wheat flour
• 2 tsp. baking soda
• 1 tsp. baking powder
• 3/4 tsp. kosher salt
• 2 tsp. cinnamon
• 1/2 tsp. nutmeg
• 1/2 tsp. allspice
• 3 eggs
• 1 cup safflower oil
• 1-3/4 cups dark brown sugar
• 2 tsp vanilla extract
• 2-1/2 cups rhubarb, diced into ¼” – ½” pieces
• 3/4 cup chopped mix of roasted almonds and walnuts
• 2 Tbsp softened unsalted butter
• 1 cup confectioners’ sugar
• 3/4 tsp vanilla extract
• 1 Tbsp milk or heavy cream