Egg wash: 1 egg plus 1 teaspoon water(beat together)
Rolled oats(for topping, optional)
In stand mixer bowl, add 1 cup bread flour, yeast, sugar and salt; mix well. In saucepan or microwave-safe dish, heat water, oil and marmalade to 120-130°F. Add to flour mixture. Using a paddle attachment, blend on low speed for 30 seconds; beat on medium speed for 4 minutes.
Switch to dough hook attachment. Gradually stir in whole wheat flour, walnuts, and enough remaining bread flour to make a firm dough. Knead until smooth and elastic, about 5 to 7 minutes.(NOTE: For hand mixing: following above steps, mix ingredients in large mixing bowl using a wooden spoon or dough whisk. Knead on floured surface until smooth and elastic.)
Prepare pan: Grease one 9x5-inch bread pan.
Turn dough onto lightly floured surface; punch down to remove air bubbles. Roll or pat into a 14x7-inch rectangle. Starting with shorter side, roll up tightly, pressing dough into roll. Pinch edges and taper ends to seal. Place in prepared pan. Cover; let rise until indentation remains after touching.Alternatively, shape dough into a round loaf, place on greased or parchment-lined cookie sheet.
Preheat oven to 375°F.
Brush risen loaf with egg wash. Sprinkle with oats, if desired. Bake for 30 to 40 minutes, until golden and internal temperature reaches 190°F. Remove from cookie sheet; cool on wire rack.