Sometimes also called Empress Plums, they are the European-style plum (Prunica domestica) - small, dense, egg-shaped fruit with blue or purple skin, freestone pits (they separate easily from the flesh) and yellow flesh. These are the plums that are made into prunes. If prunes aren't your thing, but baking is, fear not: you'll be happy to know that prune plums are wonderful sugared and cooked.
Select fruits that are more firm than you might select if eating raw. A simple dessert has you halving the plums along their indentation, toss them in sugar, flour and cinnamon and baking in individual ramekins. Top with a crumble, or simply bake and garnish with a dollop of crème fraîche.
When cooked, they turn an amazing fuchsia pink color and are not reminiscent of prunes in any way. Wait until you see the pie next week.