White Asparagus with Orange-Butter Sauce

6 oranges
2 lb white asparagus trimmed, peeled
2 tbsp white wine vinegar
Taste Kosher salt
Taste Ground black pepper
4 tbsp Butter, cold unsalted, cut up
4 tarragon leaves only

Juice five oranges over a sieve, about 1 1/2 cups. Zest one orange. Using a paring knife, remove the skin, pith, and outer membrane from the remaining orange. Carefully cut each segment away from the white membranes. This is called supreming the orange. Set segments aside. Place the asparagus in a large saute pan. Add 1/2 inch of water, and bring to a boil. Lower the heat, and steam to tenderize, about 8 minutes. Just before the asparagus are fully cooked, drain the liquid from the saute pan. Add 1/4 cup orange juice, and simmer until the asparagus are fork tender. Remove from heat. Season with salt and pepper. Cover, and steam while finishing the sauce. Meanwhile, in a small saucepan, bring 1 1/4 cups orange juice to a boil. Add the vinegar, lower the heat, and simmer until reduced to 1/3 cup. Remove from heat, and stir in butter, one piece at a time, until sauce is thick and creamy. Season with salt and pepper. Transfer the asparagus to a warm platter, drizzle with sauce, and garnish with reserved orange segments, zest, and tarragon.