In a medium pot over medium heat, melt the butter. When the foam subsides, add the garlic and onion and cook, stirring occasionally, until the onion is softened, about 8 minutes.
Add the artichokes and cook, stirring occasionally, until softened, about 3 minutes.
Add the stock and bring to a boil. Turn the heat to medium-low and cook, stirring occasionally, until the artichokes are very tender, about 20 minutes.
Transfer the mixture to a blender or food processor and carefully purée (or purée in the pot using an immersion blender).
Return to the pot, add the cream, and bring to a simmer over medium heat. Cook, stirring occasionally, until reduced by a third, about 45 minutes.
Season to taste with salt and black pepper. Serve with lemon wedges and sourdough bread on the side.
