Preheat the oven to 350° F (180°C). Line a cookie sheet with either parchment paper or a silicone baking mat. Set aside.
Cream together the butter and granulated sugar using either a stand mixer or an electric hand mixer.
1 1/2 cups (333g) salted butter, 1 1/2 cups (345g) granulated sugar
Scrape the sides of the bowl and add in the eggs, vanilla extract and canola oil.
3 eggs, 3 tsp vanilla extract, 1/4 cup (60g) canola oil
Once incorporated, add in the flour and baking powder. Mix until a soft dough forms.
4 1/2 cups (684g) all-purpose flour , 3 tsp baking powder
Portion out the dough into a generous 1/3 of a cup portions (a #12 scoop is perfect). Roll into a ball and then flatten slightly before baking.
Bake at 350° F (180°C) for 11-13 minutes or until the cookies have spread and the center of the cookie no longer looks wet and glossy.
Allow the cookies to cool completely on the pan. Once the cookies have cooled, make the frosting.
To make the frosting, slowly cream the butter until smooth.
3/4 cup (167g) salted butter
Add powdered sugar one cup at a time. Add a splash of heavy cream to the bowl to help incorporate the powdered sugar into the butter.
4 1/2 cups (482g) powdered sugar, Up to 1/2 cup (up to 120mL) heavy cream
Repeat the last step until all 4 1/2 cups of powdered sugar has been added.
Add in the vanilla extract. Add more heavy cream to thin the frosting, if needed.
3 tsp vanilla extract
Generously frost each cookie and serve chilled.