Melt the garlic & herb butter in a frying pan over medium-low heat.
Add breadcrumbs and a pinch of salt.
Cook, stirring constantly, until evenly golden and fragrant (3–5 mins).
Tip onto a plate immediately to stop browning.
Heat olive oil in a wide pan. Fry the onion or shallot with a pinch of salt until soft and sweet, 5–7 mins.
Add garlic, fry for a further 30 seconds.
Pour in single cream and a few spoonfuls of the bean stock. Stir in black pepper and lemon zest. Simmer 2–3 mins.
Add butter beans. Gently simmer 5–6 mins until glossy and thickened, stirring in more bean stock if necessary.
Serve immediately sprinkled with the breadcrumbs.