To make the dough, whisk together the butter, sugar and milk with an electric mixer until well combined and fluffy.
Whisk in the bicarbonate of soda, cinnamon, ginger, cardamom, anise, nutmeg, cloves, allspice, coriander and a pinch of salt.
Add the flour and stir with a spatula to form a soft dough.
Bring the dough together into a disc, wrap and refrigerate for a couple of hours until firm enough to roll out.
At the same time as making the dough make the almond paste - stir together the ground almonds, sugar, lemon zest and juice, milk and almond extract. Cover and refrigerate until needed.
When the dough is sufficiently chilled, preheat the oven to 180°C/160°C fan/350°F/gas mark 4. Line a 20 cm/8 in square cake tin with baking parchment.
Divide the dough into two pieces - one ⅔ rds and one ⅓ rd. Roll the larger piece out on a lightly floured surface into a square big enough to line a 20cm square tin, coming most of the way up the sides.
Press the dough into the tin and up the sides, if it tears at all just press it back together with your fingers.
Spread the almond paste evenly over the top of the dough and fold the edges over.
Brush the folded edges with milk the roll out the other piece of dough into a 20cm square.
Place the square of dough on top of the almond paste and press the edges together to seal.
Brush the top of the dough with milk and decorate as you like with blanched almonds; I like to place one in the centre of each square.
Bake for 30-40 minutes until nicely golden. Leave to cool in the tin for 20 minutes then carefully lift it out onto a wire rack and leave to cool completely.
Once cold, use a sharp knife to slice it into squares and store in an airtight container.