Blanch the dandelion greens in a pot of salted boiling water for 2-3 minutes. Dunk into an ice bath to stop cooking, strain and squeeze to remove excess water from greens. Roughly chop the dandelion greens so that they will blend more easily.
Toast walnuts in a dry pan on medium heat (do not use a nonstick pan) until fragrant. Let cool.
In a food processor, combine greens, garlic, walnuts, cheese and salt and pepper. Pulse until dandelion greens are chopped. Slowly stream in the olive oil while the food processor is running. Add a nice squeeze of lemon juice to finish.
Pesto can be used for pasta, chicken or pork. Extra pesto can be frozen in an airtight container.