125 grams unsalted butter, softened
110 grams caster sugar
1 teaspoon vanilla extract
1 RSPCA Approved egg yolk
100 grams dark chocolate, melted and cooled slightly+
150 grams plain flour, sifted
25 grams Dutch cocoa, sifted
190 grams store-bought thick caramel or dulce de leche++
+ To melt the chocolate in the thumbprint cookies, place the chocolate in a small heatproof bowl and set over a saucepan of just simmering water. Stir until melted and smooth. Set aside to cool slightly for 5–10 minutes.
++ We like to use dulce de leche when using thick caramel in desserts, which is made from cooked condensed milk. Find it at specialty grocery stores.