Preheat oven: 180°C / 160°C (fan) / Gas Mark 4 / 350°F
Melt the butter for 30-50secs in the microwave and beat in the sugar until smooth and thick.
Thoroughly beat in the egg, almond extract and salt (if using) until well combined.
Add the ground almonds, then sieve in the flour and cornflour, stirring in until combined.
Stir in the glace cherries and white chocolate chips until spread evenly throughout the mix.
Pour the blondie mix into a lined 8-inch square pan*, smoothing out gently. Using a teaspoon, dollop the jam on top, spacing the blobs out. Gently swirl them through the blondie mix with a knife or skewer.
Bake for 25-30mins until the top is lightly golden and has only a slight wobble in the middle.
Sprinkle almond flakes on top and allow your blondies to cool.
If using, in a small bowl mix the icing sugar with 2-3tsp of warm water until you get a smooth icing. Drizzle this over your cooled blondie then cut into squares and enjoy.
* You can swap the 8-inch square pan for a 9-inch square pan and reduce the baking time by 5mins.** The cornflour used in this recipe is a white fine flour, not a yellow coarse flour. However, sometimes this is called cornstarch and the yellow version is called cornflour, e.g. in the US, so be sure to pick the white one!