In a small bowl, whisk together the flour, salt, baking powder, baking soda, and cornstarch. Set aside.
In a large bowl, beat the butter with an electric mixer on medium speed for about 1 minute, until nice and creamy.
Slowly stream in the sugar to the butter, while beating constantly.
Next, add the egg and vanilla and beat until combined.
Add the dry ingredients to the wet in 3 batches, mixing between each addition.
Gather the dough into a ball, press it flat into a disk, and wrap it in plastic wrap.
Refrigerate the dough for at least 4 hours, or overnight.
When ready to bake, preheat the oven to 350.
Roll the dough out into a 12” circle on a piece of parchment paper.
Transfer the parchment paper to a baking pan, and bake the cookie pizza until set, about 18 minutes. The edges should start to turn golden brown. The center may be a bit puffy, but it will settle as it cools.
Let the cookie pizza completely cool before proceeding.
Spread the apricot jam on the pizza. Top with the chopped chocolate and slice into wedges before serving.
Use the sugar cookie crust as a base, and top with all of your favorite toppings. A cream cheese frosting with sprinkles would be a great kids’ version (or an adult that eats like a kid). If you love white chocolate, it would be great here alone, or mixed in with the dark chocolate.