Succulent white asparagus and bitter endive are braised in fresh orange juice, then topped with a sauce made of the thickened juice mixed with white wine and Grand Marnier.
Using a citrus zester, remove orange zest in very thin strips from half of the orange, and set aside. Using a sharp knife, remove and discard peel and pith from orange; cut orange crosswise into 1/4-inch-thick rounds; cut rounds into quarters, and set aside.
Snap off and discard tough ends of asparagus. Using a vegetable peeler, remove outer layer of asparagus. Melt 1 tablespoon butter in a large saute pan over medium-high heat. Add asparagus and endive; saute until endive is golden brown, about 4 minutes.
Add 5 tablespoons orange juice and 3/4 teaspoon salt; braise, covered, until just tender, about 8 minutes. Transfer asparagus and endive to plates; set aside in a warm place.
Add wine, remaining 5 tablespoons orange juice, and Grand Marnier to pan. Swirl liquid, deglazing pan. Remove from heat; swirl in remaining tablespoon butter. Drizzle sauce over asparagus and endive; garnish with reserved orange pieces and zest. Serve immediately.