Preheat oven to 375 F and place a silicone baking mat onto a baking sheet.

Beat the sugar and butter until light and fluffy. Add the eggs and vanilla extract and continue to beat until fully blended. Gradually sieve in the flour and add the salt, and beat together until all the flour is incorporated, and the dough comes together as a ball.

Split dough into 12 pieces and form balls of about 1 inch. Place onto the baking mat, evenly spaced, and flatten each one down by pressing with your thumb in the center of each cookie. This will leave a small indentation ready for filling. Kids love to help for this part, but try to encourage gentle pressing where possible. You are making thumbprint cookies after all, not thumb-flattened pancakes.

Bake for 8-10 minutes or until the bases are looking just golden. Remove from the oven and fill each with approximately ½ teaspoon of your preferred filling. Return to the oven and bake for an additional 3-4 minutes. The cookies should be lightly golden, and the filling slightly melted.

Remove and place on a cooling rack. Resist urges to scoff the lot while still too hot to touch.