Some call them French lentils, I call them Puy lentils, this packet were marked as Green lentils. Whatever they're called, as long as they are this lovely mottled blue green, they're the ones. Always look for long dates - fresh is very important with pulses. I cover them well with stock, whatever I have to hand, then bring to the boil and simmer until cooked but still with bite, how long depends on the freshness but if fresh, around 15 minutes.
I usually dress with a garlicky vinegarette, lots of herbs and eat at room temperature with something, if they survive long enough!