Prepare the Dressing
Beat shallots or scallions in a small bowl with salt and tarragon, and then beat in egg yolk, mustard, lemon juice, and vinegar. Pour in the oil slowly and whisk until it thickens. Set aside until just before serving, but whisk one more time at that point. (Note: you’ll want to make some extra dressing if you decide to dip the leaves into dressing; see below.)
Prepare the Seafood
Shell and devein the shrimp and sauté them in some olive oil for a minute or two on each side until barely done. Remove, drain on paper towels, chop each shrimp into 3 or so pieces, and put into medium-size bowl. Halve the scallops if large. Add a little more oil to the pan and sauté for a couple of minutes, turning, until barely done. Drain, and cut up a little so they are about the same size of the shrimp. Add them to the shrimp, and toss with a little salt, pepper, and lemon juice. Cover and refrigerate.
Put each half artichoke, cavity side up, on a salad plate. Whisk the dressing one more time and mix into the shellfish. You may or may not want to use all the dressing. Scoop the shellfish into each artichoke and serve soon. Guests generally eat the filling first, and then go at the leaves and heart.
To Dip or Not to Dip – and into What?
There are four ways to go here. (1) Eat the leaves without any dipping sauce, or provide little bowls with: (2) store-bought mayo, which to me is pretty delicious; (3) extra dressing from above recipe (if so, make maybe twice as much as the recipe calls for); or (4) make your own mayo.
I am partial to the last method and it couldn’t be easier with a food processer. It can be made in advance and keeps in the fridge for at least a week. Find a recipe on the Internet is simple. The main thing I want to recommend is that you NOT use virgin olive oil. For chemical reasons I don’t understand, it comes out very bitter. You can use “pure” olive oil instead, but I recommend instead that you use a neutral oil like grape seed. Typically the only other ingredients are (fantastic) olive oil, egg yolk, lemon juice, and salt.