Grease and line a 20cm square tin with baking parchment. For the shortbread, mix together all the ingredients in a large bowl with a pinch of salt until combined. Press into the prepared tin and smooth to level. Chill for 30min to firm up. Preheat oven to 180°C (160°C fan) mark 4.
Bake the shortbread for 20min, until pale golden and the edges feel firm.
Meanwhile, for the frangipane, whisk together all the ingredients in a bowl using a balloon whisk until combined.
Spread the jam over the shortbread base. Scrape the frangipane over the jam and smooth to level. Sprinkle over the flaked almonds. Return to the oven for 30min, until frangipane is pale golden. Leave to cool completely in the tin before dusting with icing sugar and cutting into slices.
