• This recipe fits into 9 x 5 inch loaf pan with at least 3 inches height.

Prepare the sweet potatoes: (recommended to prepare the night before)

• Peel the sweet potatoes and cut into 1-inch chunks. Put this in a saucepan and cover with water, about 1-inch above the potatoes and bring to a boil and then lower slightly to let it simmer for about 15 minutes or until the sweet potatoes are really fork-tender.
• Drain off the cooking liquid completely using a heat-proof colander and then transfer the cooked sweet potatoes back into the saucepan. Use a potato masher or a fork to mash it until really fine. Let this cool down completely before using. Don't use it while they are still very warm. Once it has cooled down completely, you can cover and keep them in the fridge for a few days until you are ready to use them.

Prepare the dough:

• You will only about 255 grams (about 1 1/4 cups) of the mashed sweet potatoes. You may or may not have extra of mashed potatoes. Add the mashed sweet potatoes to a mixing bowl of a standmixer. Add the rest of the ingredients for the dough. Give it a rough mix by stirring using the dough hook attachment.
• Start kneading on lowest speed for about 2-3 minutes and then increase the speed to medium (speed 4 on KA machine) for about 7-8 minutes or until the dough is smooth and elastic. You may need to reposition the dough several times throughout the kneading time.
  
• The dough should clear the sides of the bowl but still stick to the bottom.
  
• Add the finely chopped walnuts and knead on the lowest speed to distribute the walnut pieces as evenly as possible, about 1-2 minutes
  
• If you gently stretch a small portion of the dough thinly, it should stretch thinly without tearing easily
  

Proof the dough:

• Pick up the dough and give it a few kneading by hands to round it up into a dough ball. Oil the same mixing bowl all over and put the dough back into the bowl, cover, and let it proof at a warm place until it is double in volume.
  
• This take about 1 hour or longer depending on the temperature.
  

Shaping:

• Oil the bread pan all over. Transfer the dough onto a work surface. Press the dough into a 10 x 5 inch rectangle.
  
• Starting from the short side, roll down the dough to form a tight roll.
  
• The dough will elongate as you roll it down. Pinch the seams together to seal
  
• Place the log into the prepared pan, seam side down, and press with your hands to flatten the dough and to fill up the pan evenly with the dough
  

Final proofing:

• Cover with an oiled plastic wrap and let it proof at a warm place until the dough crown about 1-inch above the rim. The dough should look noticeably puffy and airy
  
• Optional: use a bread lame or razor to score a long line down the loaf, about 1/2-inch deep
  

Baking:

• 15 minutes before the end of the final proofing, start preheating the oven at 350 F (180 C) for conventional oven. If you use a convection oven, lower the temperature by 20 F (15 C)
• Place the pan in the middle rack and let it bake or 45-50 minutes, or until a digital thermometer inserted into the center part of the loaf registers 190 F. Start checking at 45 minutes. Brush with some melted butter on top right out of the oven if you wish. This is optional
  
• Loosen the bread with a flexible spatula and gently wiggle it out of the pan and let it cool on a cooling rack completely, this may take 2-3 hours or longer. Do not slice into a warm bread
  

How to store:

• The completely cooled down bread can be kept at room temperature for about 3 days or longer (if it's not humid where you are). Keep them in an air-tight container or well-wrapped to prevent it from drying out
• You can also keep the sliced bread well-wrapped and stored in a freezer bag, in a freezer for up to 1 month. Simply thaw at room temperature before using. A quick reheat in the air-fryer or toaster oven at 320 F for 4-5 minutes makes it "new" again