Combine avocado, basil, 4 tsp lemon zest ... adding a little water if needed to achieve a sauce-like consistency. Season with salt or lemon juice to taste.

Though some pesto cream sauce recipes require heating ... I recommend using a food processor for it, but it could also work in a blender. Combine basil, garlic, pine nuts, and lemon juice (if using) ...

Tip it into the slow cooker, along with the remaining stock. Add the lemon zest and basil and season with salt and pepper, then give everything a good stir. Spread the courgettes over the top of ...