• Preheat the oven to 350°F (180°C).
• In a stand mixer or with an electric hand mixer, cream together the butter, brown sugar, and sugar until light in color and fluffy in texture.
  3/4 cup (167g) salted butter, softened , 3/4 cup (185g) brown sugar, 1/4 cup (58g) granulated sugar
• Scrape the sides of the bowl and add in the egg and canola oil. Mix until well combined.
  1 egg, 1 Tbsp canola oil
• Add the flour, rolled oats, cornstarch, cinnamon, baking soda and salt. Mix until the dough forms.
  1 1/2 cup (228g) all-purpose flour, 1 1/2 Tbsp cornstarch, 1 1/2 cups (150g) rolled oats, 1 tsp cinnamon, 1 tsp baking soda, 1/2 tsp salt
• Loosely press the dough into a greased 9x13 pan leaving the top textured.
• Bake at 350°F (180°C) for 15-17 minutes or until the center no longer looks wet and glossy.

Icing

• While the cookie bars are baking, make the icing by combining the butter and shortening until smooth.
  1/4 cup (56g) salted butter, softened , 1 Tbsp vegetable shortening
• Add in the powdered sugar, vanilla and 1 tbsp of milk. You can always add more milk, if needed. The icing should be quite thick.
  1 1/2 cups (161g) powdered sugar, 1 tsp vanilla `, 1-2 Tbsp milk
• Transfer the icing to a zip top bag with the corner clipped or piping bag.
• Immediately after the bars come out of the oven, zig zag the icing on top of the cookie bars. Allow the icing to melt and then use a spoon to push the icing to fill up all the dips in the texture on the top of the cookie bars.
• Allow the bars to cool completely in the pan. Cut and serve.
• Enjoy!