Preheat and Prepare: Preheat your oven to 180°C (160°C fan). Grease a 20cm square or similar-sized baking dish with a little butter. The warmth of the oven will soon be the heart of your kitchen.

Make the Berry Filling: In a large mixing bowl, combine the 600g of berries, 60g powdered erythritol, 2 tablespoons arrowroot powder, 1 teaspoon vanilla extract, and 1 tablespoon lemon juice. Gently toss everything together with a rubber spatula until the berries are evenly coated. You will see the pale powder clinging to the bright fruit, and the tart, fruity scent will immediately lift your spirits.

Create the Almond Crust Topping: In a separate bowl, whisk together 150g almond flour, the chopped nuts, 1/2 teaspoon cinnamon, 1/4 teaspoon sea salt, and a pinch of nutmeg. Add the cold, diced butter and the egg yolk. Using your fingertips, rub the butter into the dry ingredients until the mixture resembles coarse breadcrumbs with some larger, pebbly bits. It should feel cool and crumbly, with a rich, buttery fragrance.

Assemble the Crisp: Pour the berry mixture into the prepared baking dish, spreading it into an even layer. You will hear the soft thud of the fruit settling. Sprinkle the almond crust topping evenly over the berries, covering them completely but leaving some gaps for the filling to bubble through.

Bake to Golden Perfection: Place the dish in the preheated oven and bake for 28-32 minutes. You will know it is ready when the topping is a deep golden-brown and the berry juices are bubbling visibly around the edges, releasing a glorious, caramelised aroma. The kitchen will smell like a cosy bakery.

Rest and Serve: Remove the crisp from the oven and let it rest on a wire rack for at least 10-15 minutes. This crucial step allows the filling to set, preventing a runny mess. The berries will continue to gently cook in the residual heat, creating a luscious, jammy texture. Serve warm.