I made an enormous batch of these this morning for the photo but when I went to get one to go with my cup of tea they had all gone. If you are not a jam fan fill the thumb print with a whole almond, a glacé cherry or just leave them plain.
225g self raising flour
100g caster sugar
125g butter, chilled and diced
½tsp vanilla extract
raspberry, strawberry, apricot or blackcurrant jam
caster sugar for sprinkling
Sift the flour into a large bowl with the caster sugar. Add the butter, rubbing the it into the flour and sugar by pinching and lifting the mixture with the tips of your fingers until it looks like fine breadcrumbs or sand. Crack the egg into a cup, add the vanilla extract and stir to combine. Add the beaten egg and mix together to a soft dough.
Divide the dough into 16 equal pieces and roll each piece into a ball. Arrange the balls well apart on greased baking sheets. Dust your thumb with flour and gently press into the middle of each ball of dough to make a small hole. Then place a half teaspoonful of jam in the centre of each hole.
Cook the biscuits at 180°C for 15min or until golden. Sprinkle with caster sugar and then transfer to a wire rack to cool.