To make the base layer, add the almonds and oats to a food processor and blitz until you have a fine crumb like mixture. Add the rest of the base ingredients and blitz until you have a sticky mixture that sticks together when compressed.

Line a 8 inch x 6 inch baking tray with greaseproof paper and firmly press the base mixture into the tin so it is completely flat and compressed. Place in the freezer.

Rinse out the food processor then put in the frozen raspberries and strawberries. Blend on a high speed, scraping down the sides regularly until the mixture is completely smooth and has the consistency of soft serve ice cream. You need to be patient with it - this process does take some time, but just keep going and scraping and it will get there. Once it's smooth, add the maple syrup and chia seeds and blend again so everything is evenly combined.

Remove the base from the freezer and spread the sorbet mixture over the top. Sprinkle over the seeds and place back in the freezer for a minimum of 4 hours.

When ready to serve, remove from the freezer, let sit at room temperature for about 15 minutes and then cut into bars. If desired, drizzle with dark chocolate.

Store the bars in the freezer, and let sit at room temperature for 5-10 minutes before eating.