In a bowl, combine the artichokes with the smashed garlic, 2 tablespoons of the olive oil and the lemon juice; season with salt and pepper. Refrigerate for up to 1 day. Discard the garlic.
Cook the sugar snap peas in boiling water until just tender, about 5 minutes. Using a slotted spoon, transfer them to a colander set under cold running water; drain. Repeat with the fava beans, cooking them for 2 minutes. Peel the beans, then add them to the peas.
Heat a 12-inch skillet.
Add the artichokes in a single layer and cook over high heat, turning once or twice, until golden, about 8 minutes.
Transfer the artichokes to a large bowl. Repeat with the snap peas and fava beans, cooking them for 3 minutes; add to the artichokes.
Cook the pasta in a stockpot of boiling salted water until al dente.
Drain well, reserving 1/2 cup of the cooking water; add the pasta to the vegetables.
Meanwhile, heat the remaining 3/4 cup of olive oil in the skillet.
Add the chiles and sliced garlic and cook over high heat, stirring, for 2 minutes.
Add the shrimp, scallions and tarragon, season with salt and pepper and cook, stirring, just until the shrimp turn pink.
Add the wine and cook, stirring, for 2 minutes, then pour over the pasta and toss; add some of the cooking water if the pasta looks dry. Season with salt and pepper and serve.
