Preheat the oven to 350F.
Sift cornstarch, flour, baking powder, baking soda and salt together in a large mixing bowl. Set aside.
In a stand mixer fitted with a paddle attachment, cream the butter and sugar together.
Pour in the egg yolks and vanilla extract and beat for 5 minutes on a low speed.
Add the dry ingredients to the mixer and beat until a crumbly dough forms.
Add the heavy cream and beat until the dough comes together.
Turn the dough onto a well-floured surface and form into a ball. Flatten into a disc and wrap in plastic wrap. Refrigerate for 1 hour.
Take the dough out of the fridge and place on a well-floured piece of parchment paper. Let it soften at room temperature for 15 minutes.
Using a floured rolling pin, roll the dough out to a 1/4-inch thick. Using a 2-inch round cookie cutter, cut the dough into rounds.
Place the finished cookies on a large baking sheet lined with parchment paper or a silicon baking mat. Refrigerate for 15 minutes before placing in the oven.
Bake the cookies for 15-20 minutes or until golden brown. Transfer to a cooling rack and cool completely.
To assemble the cookies, place a 1/2 teaspoon of meyer lemon curd on the base of one cookie. Place a fresh mint leaf on top of the curd and take another cookie to create a sandwich.
Dust the finished cookies with confectioner's sugar and enjoy.