In a hot sauté pan over medium heat, toast the nuts or seeds for about one minute being careful not to burn. Remove from heat and set aside.
With garden or kitchen gloves, remove the nettle leaves from stems.
Bring 1 to 2 inches of water to a boil in a large sauce pan fitted with a metal steamer basket. Drop the nettles into the basket with tongs, cover and steam for 5 minutes. Remove the steamed nettles and place in a bowl of ice water.
After the nettles have cooled, remove by the handful and squeeze out the excess water in a dish towel.
In a food processor, blitz the nuts and garlic with a tablespoon of olive oil until smooth.
Add the nettles and lemon juice, blitz thoroughly (optionally you can also add a handful of arugula leaves for a peppery version).
With the blender or food processor running, slowly pour in the remaining olive oil until you reach your desired consistency.
Use immediately, refrigerate or freeze.