Preheat oven to 350°F and line your baking pan with parchment paper.
In a large mixing bowl cream your butter, sugar and brown sugar until light and fluffy.
Add your vanilla extract and egg, and stir until well combined.
Add your flour, cornstarch, baking soda, and salt. Stir until just combined.
Scoop your cookie dough into your lined baking dish and press down until it’s even using your hand or a spatula.
Bake in the oven at 350 F for 8-10 minutes until edges start to brown.
Remove from oven and let cool.
In a bowl of a mixer add your butter, and whip up until fluffy. Add you powdered sugar, heavy cream, and vanilla and whip until well combined and smooth. (If your frosting is too thin, add a little more powdered sugar and if it’s too thick add a little more.
Top with buttercream frosting and spread evenly. Top with crushed Easter candy or spring colored sprinkles.
Cut into bars!! Serve, share & Enjoy!!