In a mixer bowl, beat together butter and sugar until creamy. Add egg yolks, lemon peel (if desired), vanilla, almond extract and salt; beat well.
Mix in flour and ¼ cup of the nuts until blended. Gather into a ball, cover in plastic wrap and refrigerate 1 hour.
Heat oven to 190°C. Lightly coat baking sheet with non-stick spray or line with parchment paper.
Shape dough to form 3 cm balls; roll into remaining 1 cup of nuts to coat lightly. Place 50cm apart on baking sheet.
Using your thumb or a wooden spoon handle, make a depression in each cookie. Fill each with scant ½ teaspoon jam or curd. Bake 20 - 25 minutes or until golden.
Cool on a baking sheet 5 minutes; sprinkle with icing sugar if desired. Transfer to wire racks and cool completely. Store in an airtight container.
Food process your favourite chopped nuts into a fine nut meal, this will make covering in nut mixture more successful.
Resting the mix in the fridge is important.
Even in the winter, store nuts in an airtight jar and keep in the fridge. Buy small amounts of nuts often rather than larger quantities.
Leave the cookies on the tray for a few minutes before transferring to wire rack. They’re so much easier to handle that way.
If for any reason the airtight container was left open, pop the cookies back into the oven for another bake. As soon as they look a little more golden, they are ready. The “colour” in a cookie – always transfers to flavour – especially important with shortbread.