Preheat the oven to 375 degrees F (190C).
Firstly, sift the flour, cornstarch and salt in a bowl. Set aside
Next, in an electric mixer that has a paddle attachment, cream together the butter and sugar until they are light and fluffy.
Add the eggs and blitz till blended well. Scrape down the bowl.
Now, on low speed, add the flour mixture to the creamed butter and sugar.
Mix until it becomes a dough texture. Add the vanilla extract.
Roll the dough into 1 1/4-inch ball.
Place these balls on a cookie sheet and press a light indentation on each with your thumb.
Drop 1/4 teaspoon of jam into each hollow.
Bake for about 10 minutes at 375F (190C).
Cool and serve.
For the Glaze
Add a cup of powdered sugar into a medium bowl. Add two tablespoons of milk and whisk together. Add a teaspoon of vanilla or any flavouring you like. Once the cookies have cooled you can drizzle the glaze over them.