Beat the butter and sugar at high speed with an electric mixer until pale and fluffy. Add the beaten egg and the almond essence and beat for another minute. Fold in the flour, ground almonds and toasted walnuts (or hazelnuts). The dough should be soft. If time permits, refrigerate the dough for about 30 minutes so that it is easier to handle.
Preheat oven 180 C. When you are ready to make the biscuits, take small spoonfuls of the dough and shape into round balls. Place these on a lined baking sheet. Press the balls with the bottom of a flat glass to make a flat disc. These should be about 4 mm deep. Make sure you apply even pressure so that the thickness of the circle is the same. This will ensure the cookies bake evenly. If the dough is too sticky then dip the bottom of the glass in a little gf flour or better still stick the dough in the freezer to harden up a bit. Continue this process until all the dough is used up. Bake the cookies for 12- 15 minutes until lightly golden and crisp. Allow the biscuits to rest a few minutes on the baking sheet before placing them on a wire rack to cool.
Alternatively, you can shape the dough into a log and wrap it in greaseproof paper. Allow this to chill for about 2 hours. When you are ready to make the biscuits, use a sharp knife to cut slices about 4mm thick. Place these on a lined baking sheet and bake as above.
These cookies are really versatile. They are great with a cup of tea or hot chocolate and delicious dipped in chocolate mousse! Serve them alongside ice cream or sorbet.