Leaf curd (or leaf concentrate) is the name for extracted plant proteins from edible plant leaves.
In many places where animal protein consumption is not appropriate, finding alternative low-cost plant-based proteins can be very problematic. Whilst some cultures have a history of using tofu - bean curds - these are not universally accepted for consumption.
Very generally, the process involves breaking up plant leaves manually, then bringing the mash to the boil in a boil of water. The proteins can then be scraped off the surface of the water and excess water removed.
Leaf for Life have been working for some time on developing models for production of leaf curd at various scales
Fergus Drennan has a photo blog showing how he used and adapted these methods on a kitchen scale