Finely grate zest from half of an orange; set zest aside. Using a sharp paring knife, cut peel and white pith from oranges, then cut each section of fruit away from membranes, cutting as close to membranes as you can, and place sections in a bowl. Remove white pith from 1 piece of peel, then thinly slice peel; set aside.

Place butter pieces in a 4-cup glass measuring cup. Microwave on high 2 minutes. Remove from microwave and let stand 1 minute. Spoon off foamy top layer. Spoon clear (clarified) butter into small bowl. Discard any milky liquid at bottom of measuring cup.

Steam vegetables in batches until crisp-tender; set aside.

In a small saucepan, heat orange juice over medium heat, just until warm. Whisk in yolks, then cook over very low heat, whisking constantly, until thickened (be careful not to scramble yolks), about 1 minute. In a slow and steady stream, whisk in butter, lifting pan occasionally to cool sauce. Add reserved zest; season to taste with salt.

Arrange vegetables and oranges on serving plates. Drizzle with sauce, sprinkle with pepper, and garnish with sliced orange peel.