1. Bring a medium saucepan of water to a boil. Add 3 tablespoons of the lemon juice to a large bowl of water. Working with one artichoke at a time, pull off the dark outer leaves and trim 1/2 inch off the top. Halve each of the artichokes, then drop them into the lemon water.
2. Drain the artichokes and blanch them in the boiling water until tender when pierced with a knife, about 3 minutes. Drain well.
3. Meanwhile, melt 1 teaspoon of the butter in the oil in a large nonreactive skillet. Add the garlic and cook over high heat for 10 seconds. Add the artichokes, season with salt and pepper and cook, turning once, until golden brown, about 5 minutes. Stir in the remaining 1 tablespoon of lemon juice and 1 teaspoon of butter and serve.