In a medium bowl, whisk together the flour, baking powder, salt and cinnamon.

In a food processor, pulse the almond paste and granulated sugar until finely crumbled. Add the softened butter and eggs, then process until combined, scraping down the bowl as needed.

Add the flour mixture and pulse just until the dough begins to come together. Turn onto a clean work surface and gently press any loose crumbs into the dough. Avoid kneading.

Divide into four equal portions. Wrap each portion and refrigerate for 30 minutes.

Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.

On a lightly floured surface, roll each portion into a log about 10 inches long. Place two logs on each baking sheet, leaving at least 3 inches between them. Gently flatten each log to approximately 2 inches wide.

Bake for 12–15 minutes, until the dough looks set but is still pale. If baking both sheets together, rotate them and switch their rack positions halfway through.

Remove the sheets from the oven. While the logs are warm, gently press a shallow groove along the centre of each with the back of a small spoon or a wooden spoon handle. Leave a border at both ends and avoid pressing through to the parchment.

Stir the jam to loosen it, then spoon 2 tablespoons into each groove, spreading it evenly without overflowing.

Return to the oven for 8–10 minutes, until the edges are lightly golden and the centres look set. Allow about 25 minutes of baking altogether.

Let the logs firm up on the baking sheets for 10 minutes, then carefully transfer them with a wide spatula to a wire rack. Cool completely before glazing.

Whisk the icing sugar and milk together until smooth. Drizzle over the cooled almond jam bar logs.

Let the glaze set for about 20 minutes, or until firm. Using a serrated knife and a gentle sawing motion, cut each log into 8 bars to make 32 bars.