Cut the bottom 1/2-inch off of each head of endive. Remove the nicest 6 outer leaves from each one, and set aside. With the remaining endive heads, cut them into thin strips. Remove any endive "core" that may have slipped into your nice endive ribbons. Combine your endive ribbons with the outer leaves in a large salad bowl.
Add your spinach leaves to the large salad bowl.
Split the vanilla bean in half. Scrape the seeds from the vanilla bean. (chances are, you want to save the pods. You can use them to flavor a cream at a later point) Place the vanilla beans into a small mixing bowl.
Peel the very outer layer of the lemon. You want just the very outer yellow layer, not the white "pith". Peel off nice strips with a vegetable peeler. Slice the strips into very thin noodles.
Boil a small amount of water. Add your lemon zest to the boiling water and boil for 30 seconds. Strain out the zest and set aside. This act kills a lot of the bitterness that can come from fresh lemon zest. It mellows it.
Cut your lemon in half and juice it into the bowl, with the vanilla. Add your lemon zest strips, as well.
Add 3 tbsp of the oil to the lemon juice. Whisk the mixture together and season with a little salt and pepper. Set aside.
Pre-heat a sauté pan, over medium-high heat.
Verify the "foot" has been removed from your scallops. Remove this, if it hasn't. Season your scallops with salt and pepper.
On a nice clean face, place each scallop into the sauté pan, carefully and deliberately. Let them sear in the hot pan for about 2 to 4 minutes. Do not let them touch one another and do not let them "boil or steam". You should get a nice dark "sear" on the surface area of the scallops.
Once one side is nice and golden, flip them and sear on the opposing side for a further 2 minutes. A good scallop should be rare to medium-rare (in my opinion), or else they get rubbery, quickly. They should be soft, sweet and clean.
Right as they are just perfectly cooked, add your poppy seed-lemon vinaigrette to the pan. This will deglaze the pan. Toss everything together in the pan for about 10 seconds.
Dump the contents of the sauté pan into the large salad bowl. Toss everything together, with a little salt and pepper. The hot scallops and vinaigrette will cause a very light "wilt" of the lettuce.
Remove the 12 outer leaves and make a nice fan shape on 4 plates.
Take the endive-spinach mixture and make 4 nice piles in the center of each plate.
Divide the scallops around the leaves, on each plate.
Drizzle any remaining vinaigrette in the bottom of the salad bowl, over the top of the greens and scallops.