Jane Grigson’s Walnut Bread from Southern Burgundy

Name: Jane Grigson’s Walnut Bread from Southern Burgundy
Ingredients: Jane Grigson’s Walnut Bread From Southern Burgundy (for 4 small round loaves, each about 7-inches in diameter); 5 teaspoons of Instant Dry Yeast; 1/2 cup of Milk for proofing the yeast, plus 1 and 1/2 cups of Milk to make the dough; 5 cups of Unbleached White Flour, plus a very little flour to sprinkle on the pastry board when forming the loaves; 2 Tablespoons of Sugar; 1 Tablespoon of Salt; 4 ounces (8 Tablespoons) of Butter, melted and cooled, plus a little Butter to streak the baking sheets before lining them with parchment paper; 3/4 cup of Yellow Onion, finely chopped; 1/2 cup of Walnuts, chopped; Equipment; a Bowl for proofing the yeast; a Liquid Measuring Cup with at least a 2-cup capacity; a small Pot for heating the Milk; 2 Baking Sheets lined with Parchment Paper; Parchment Paper