Preheat your oven to 350°F (175°C) and grease a heart-shaped baking pan.

In a large bowl, beat the softened unsalted butter with light brown sugar and granulated sugar until light and fluffy, about 2-3 minutes.

Add the egg and vanilla extract, mixing until well combined.

In a separate bowl, whisk together flour, cornstarch, baking soda, and kosher salt. Gradually add to the wet mixture, mixing until just combined.

Fold in semi-sweet chocolate chips, chocolate chunks, and M&M’s.

Pour the batter into the prepared pan and bake for 20-25 minutes or until edges are golden brown and a toothpick comes out clean.

Let the cake cool completely in the pan before transferring it to a wire rack.

In a clean bowl, beat softened butter until creamy.

Gradually mix in powdered sugar and heavy whipping cream, then add vanilla extract and beat until fluffy.

Add a few drops of pink gel food coloring and mix until desired shade is achieved.

Spread a generous layer of frosting over the cooled cake.

Decorate the top with pink and white heart sprinkles.