Step 1In a medium, heavy-bottomed pot heated over medium-high heat until hot, melt 6 tablespoons butter. Add the onions and saute until they begin to brown, 6 to 8 minutes, stirring frequently. Stir in the garlic and peppers, and continue to cook until the garlic is aromatic, 1 to 2 minutes.
Step 2Add the sherry and stir, scraping any bits of flavoring from the base of the pot. Stir in the artichoke hearts, chicken broth and sugar. Season with one-fourth teaspoon salt, or to taste.
Step 3Bring the mixture to a boil over high heat, then reduce the heat and simmer, loosely covered, for 30 minutes.
Step 4While the soup is simmering, make a roux: In a small saucepan, melt the remaining 4 tablespoons butter over medium heat. Slowly rain in the flour and stir to form a roux. Continue cooking, stirring frequently, until the roux turns a light brown color, about 2 minutes. Remove from heat. This makes about one-fourth cup roux, more than is needed for the remainder of the recipe. The roux will keep, up to 2 weeks, covered and refrigerated.
Step 5When the soup has simmered for 30 minutes, uncover and slowly whisk in the cream. Thicken as desired with roux, whisking in 1 tablespoon at a time; you may not use all the roux.
Step 6Blend the soup using a stand or immersion blender, and strain if desired. Return the soup to the pot, adjust the thickness with additional roux (to thicken) or broth (to thin), and taste once more for seasoning. This makes a scant quart of soup.