Roughly chop the garlic and add it to the mortar and pestle. Add the sea salt and tarragon leaves and press and grind to break down the garlic and tarragon and a thick paste has formed.
Transfer the garlic paste to a small bowl and add the egg yolk. Use a whisk to combine the herb mixture with the egg yolk. Add the olive oil to the vegetable oil and very slowly drizzle the oil into the egg mixture, whisking constantly to form an emulsion. Do not add the oil to quickly or the emulsion will break. TIP: Whisk in ONE DIRECTION ONLY. It will take anywhere from 5-7 minutes to add all of the oil into the aioli. Just be patient and whisk and drizzle until it's completely blended and the aioli is thick.
Squeeze a few drops of lemon juice into the aioli and whisk to combine. Continue adding the rest of the lemon juice from the half of lemon a little at a time, until well blended. Taste for seasoning and adjust as necessary. Cover and refrigerate.
TRIM THE ARTICHOKES:
Cut the stem from each artichoke with a sharp knife, leaving about 1/2" - 3/4" stem remaining. Use a vegetable peeler to peel the outside of the tough fibrous stem down to the more tender interior. Remove the tough outer leaves near the stem of the artichoke and discard.
Use a pair of kitchen sheers to to cut the end of each petal of the artichoke by about 1/2" so that the spiny tips are flattened and straight. Trim away the top inch of the artichoke using a heavy, sharp knife.
FOR STOVETOP ARTICHOKES:
Add 2-3 cups of water to a large pot (large enough to fit the whole artichokes). Cut one lemon in half and squeeze the juice into the water. Add the lemon halves to the water and set a steamer basket over the water. Add the artichokes to the steamer basket and cover tightly with a lid. Bring to a boil and steam the artichokes for 40 minutes or until tender (you can tell if it's tender by sticking a sharp knife into the center of the artichoke from the bottom. If the knife goes in and out easily, it's done.
FOR INSTANT POT/PRESSURE COOKER ARTICHOKES:
Add 1-2 cups of water to the pressure cooker. Add the lemon juce and squeezed lemon halves. Fit a steaming rack over the water. Place the artichokes in the steamer basket and secure the lid. Bring to high pressure and cook for 8-9 minutes (1-2 minutes longer for very large artichokes). Let the pressure release naturally
Use a pair of tongs to lift the artichokes from the basket and transfer to a sheet pan. Let the artichokes rest for a few minutes to cool.
PREP ARTICHOKES FOR THE GRILL:
Slice the artichokes in half through the stem. Use a spoon to remove the fuzzy choke and discard. Remove the purple interior leaves and discard. Brush the interior of the artichokes lightly with remaining one tablespoon of olive oil.
Don't soak the wood chips. They should be DRY. Have a squirt water bottle available for any flareups with the wood chips. Place the wood chips in the smoker box and place over the heat on the grill. Heat the grill to about 450°. When the wood starts to smoke, add the artichokes, cut side down opposite the smoker box -- over direct heat. (Note: since the wood hasn't been soaked, it may catch fire. Use the squirt bottle to tamp down any flames.
Grill the artichokes for about 4-5 minutes, then use a pair of tongs to flip the artichokes and continue cooking for another 2-3 minutes until they've achieved a light char and smoke flavor. Transfer to a platter and serve with the tarragon aioli on the side.
To eat the artichokes, peel off each petal and dip the tender interior into a bit of aioli. Put the tender portion (the part closest to the stem) in your mouth and scrape off the soft bits with your front teeth -- getting a little aioli with each taste. Discard the petals and continue to work your way through the artichoke. Note: The artichoke heart and stem are edible and should be the most tender part of the vegetable. Add a bit more aioli to them and enjoy.