• Gather all the ingredients. You will need parchment paper and a bamboo sushi mat. In Japan, we use a special bamboo mat with thicker strips called onisudare, which gives big ridges/indentations to datemaki.
  
• Preheat oven to 400 ºF (200 ºC). For a convection oven, reduce cooking temperature by 25ºF (15ºC). Line an 8-inch x 8-inch (20cm x 20cm) baking dish with parchment paper.
  
• Cut the hanpen into ½-inch (1.3 cm) cubes and whisk eggs in a small bowl.
  
• In a blender or food processor, put the hanpen and all the seasonings (2 Tbsp mirin, 1 Tbsp sake, 1 Tbsp sugar, 1 tsp honey, and ½ tsp soy sauce).
  
• Add the beaten egg and blend until smooth, about 1 to 1.5 minutes.
  
• Strain the egg mixture through a fine sieve into a clean bowl.
  
• Then pour the mixture back into the blender and strain one more time into the bowl. Finally, pour the mixture into the baking dish lined with parchment paper.
  
• Bake at 400 ºF (200 ºC) for 20 minutes or until slightly brown on top. If the top is not golden brown, switch to a broiler and broil for 2 minutes or until the surface is golden brown. The center of the omelette will rise slightly as the top gets brown. It will shrink as it cools.
  
• Remove the baking dish from the oven and let the omelette deflate and cool to handle, just for 1-2 minutes (DO NOT LEAVE IT more than that). We will need to roll the omelette while it’s still hot.
  
• Transfer the omelette from the baking dish to a working surface by lifting the parchment paper. Then place the bamboo mat over the omelette, with the flat bamboo side facing up.
  
• Carefully flip the omelette and remove the parchment paper.
  
• Carefully score the omelette ⅛-inch (3 mm) deep for every ½ inch (1.3 cm). The knife should be parallel to the bamboo sushi mat direction. This incision will help the omelette roll up without breaking/cracking.
  
• Roll the omelette into a tight cylinder.
  
• Secure the bamboo mat roll with rubber bands and wrap it with plastic wrap. Let cool completely for 2-3 hours.
  

To Serve and Store

• Carefully remove the datemaki from the bamboo mat. Cut into 12 equal slices, about ¾-inch wide pieces. Serve at room temperature.
  

To Store

• You can keep the leftovers in an airtight container and store it in the refrigerator for 4-5 days.