• Preheat the oven to 350℉/180℃. Grease a 9" heart shaped cake pan.
• In a large bowl/the bowl of a stand mixer (with the paddle attachment), add the butter and sugar and beat together until pale and fluffy (about 3 minutes). Add the egg and egg yolk (separate in a different bowl, just in case it breaks) and mix again until fully combined.
• In another bowl, combine the flour, cornstarch and baking soda. Add to the cookie dough and beat to combine. Finally, add the chocolate chips and mix.
• Press this cookie dough into the prepared pan and add the M&Ms on top, pressing in gently. You may find it easier to press the cookie dough into the pan using your hands.
• Bake 23-26 minutes, until just golden. Remove and let cool fully.

For the Frosting

• To make the frosting, add the butter to a large mixing bowl. Beat with a whisk on high for a minute to soften.
• Add half the powdered sugar, whisk on high. Then add the remaining half with the vanilla extract and cream and whisk everything on high until fluffy. Add powdered sugar/cream as required to meet your desired consistency - it should be spreadable/fluffy.
• Add a few drops of pink food color. Note: If you want multiple shades of pink frosting like I used, start with making the lighter shade. Then remove half the frosting from the bowl and set aside before adding more food color to the remaining frosting.
• Pipe the frosting however you like and decorate with sprinkles/more candy!