Preheat 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 , 3/4 cup (200g) brown sugar, 1/4 cup (60g) 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 cups (228g) all-purpose flour, 1 1/2 cups (153g) old fashioned rolled oats, 1 1/2 tbsp cornstarch, 1 tsp cinnamon, 1 tsp baking soda, 1/2 tsp salt
Portion the dough out -For small cookies, use 1 1/2 tbsp of dough for each cookie. For larger cookies use 3 tbsp of dough.
Arrange on a silicone or parchment paper lined cookie sheet.
Bake at 350° F (180° C) until The cookies spread slightly and no longer look wet and glossy on top. Small cookies: 8-10 minutes. Larger cookies: 9-11 minutes.
Allow the cookies to cool on the pan for 5-10 minutes before serving.