The lemon does everything. Good cream, a measure of sugar, and the juice of ripe lemons. That is the whole recipe. The acid in the citrus reacts with the cream and sets it into something silken, wobbly, and impossibly rich. No eggs. No gelatin. No fuss. This is cooking that gets out of the way.

I first had posset in England, served in a small pot with nothing but a few berries on top. The restraint struck me. Americans would have added a cookie, a sauce, a garnish, something to justify the price. But the English understood: when the ingredients are right, you need nothing else.

Seek out lemons that feel heavy for their size, with thin skins that yield slightly to pressure. These will be juicy and fragrant. The cream matters too. Find cream from a local dairy if you can, something that tastes of grass and pasture rather than the industrial nothing of most supermarket cartons. Your choices shape the food system, even in dessert.

The raspberries should be bought the day you serve them. Look for berries that are deeply colored but not soft, with a perfume you can smell before you taste. If raspberries are out of season, wait. Or use whatever fruit is at its peak: sliced strawberries in June, blackberries in August, blood orange segments in winter. Let things taste of what they are.