Heat the butter in a pan and sweat the onion and garlic for about five minutes without colouring. Add the peas, potato, stock and herbs and bring to the boil. Simmer for five to six minutes until the peas are tender.
Remove and discard the herb stalks and liquidise the soup in a blender until completely smooth. Return to the heat, season and pour in the single cream. Do not allow to boil. Serve in bowls, crumbling a little feta on top.
Freezing and defrosting guidelines
Make the soup, then leave to cool at room temperature. Freeze (without garnishes or toppings) in a rigid container, leaving a bit of space for expansion, for up to 1-3 months. Reheat either from frozen or defrost in the fridge overnight. Once piping hot, add toppings or garnishes and serve.