Identify how you’re using double cream: cold topping (thickness matters most) or cooked into a sauce (heat tolerance matters most).
Choose the closest match from the list above, then swap using the listed ratio.
If your substitute is thicker (Greek yogurt, crème fraîche), warm it gently first; if it’s thinner (half-and-half), reduce longer or whisk in a small amount of cornflour/starch.
Add dairy off the boil (or lower the heat to a simmer) to reduce the chance of splitting or curdling.
Taste and adjust: add salt/seasoning to bring flavor forward, and a splash of milk/water only if the sauce becomes too heavy.