In its native Morocco, this tasty soup is often eaten as a hearty workers’ breakfast, served from street stalls and hole-in-the-wall cafés. With such a simple pulse-based dish, getting the seasoning right is absolutely key to elevating it from potentially bland to really sublime, and here a sprinkle of spice and a good drizzle of lemon and garlic oil make this soup sing.
Make the lemon and garlic oil by adding 200ml olive oil, the lemon rind and the sliced garlic to a small, heavy-based saucepan set over a low heat. Allow the oil to warm very, very gently for 30 minutes. It should not boil, just slowly putter away with the odd tiny bubble breaking the surface. Remove from the heat and leave to infuse until you are ready to serve.
In a large, heavy-based saucepan, toast the cumin seeds and chilli flakes over a medium-low heat. As soon as you can smell their aroma wafting up from the pan, tip them into a pestle and mortar and grind coarsely.
Place 2 tablespoons olive oil in a pan along with the onion and set over a low heat to soften gently without colouring. This will take a good 30 minutes, so be patient. When the onion is meltingly soft, add the crushed garlic and half of the ground spices and cook for a further couple of minutes.
Add the split peas, pour over the stock and bring to the boil. Reduce the heat a little and simmer steadily until the peas are soft and collapsing. Purée the soup until velvety smooth, using either a stick blender or a liquidiser. Season to taste with salt and pepper and keep warm over a low heat.
Strain the lemon and garlic oil through a fine sieve and discard the lemon rind and garlic slices. The oil will keep in a clean covered jar for at least a couple of weeks
Serve the soup in deep bowls or mugs, sprinkled with the remaining spices and drizzled with the lemon and garlic oil.