• Preheat the oven to 350 F / 176 C
• Line 2 12-cup standard muffin pans with muffin liners or grease with unsalted butter
• Roast the raw walnuts on low-medium heat until they are a little darker and crispy
  

Step 1: Streusel Topping

• In a small to medium-sized bowl, whisk together flour, tapioca starch, oats, sugars, cinnamon, and salt.
• Add walnut oil and butter, then mash the mixture together with a fork until the butter is evenly incorporated and looks clumpy, like smashed peas.
  
• Set aside in the refrigerator until you need to use it.
  

Step 2: Dry Mix

• In a medium sized mixing bowl, whisk together flour, tapioca starch, oats, sugars, salt, baking soda, and baking powder until well combined.
  
• Toss in the chopped walnuts and mix until evenly incorporated.
  

Step 3: Wet Mix

• In a separate, larger bowl (or KitchenAid bowl), beat (or whisk) the eggs and granulated sugar on high for about 5-7 minutes. The mixture will be fluffier and pale. When the whisk is lifted out of the bowl, the mixture makes lovely "ribbons" or trails.
  
• Add the walnut oil and buttermilk and gradually increase to high so as not to splatter everywhere. Mix on high for 1-2 minutes.
  
• Now peel, measure and mash the bananas, in a separate bowl. You can use a fork or fingers, just don't mash it up too much. Add to the wet mix, and mix briefly on high until it is well incorporated.
  

Step 4: Combine Mixes

• Tip! Be careful not to over mix the dry ingredients into the wet mix. (You don't want to lose all the air you got from whisking those eggs!)
• Gradually (I like to add the dry mix in 3 rounds) and gently add the dry mixture to the wet mixture. Ideally, it should be more like a folding motion rather than a mixing or stirring one.
  
• It's better to have a little dry mix still lumpy than to over mix.
  

Step 5: Scoop & Streusel It

• I like to use a medium-sized ice cream scooper to scoop the batter into the muffin liners. I'll add a scoop to all the cups, and then add then try to add evenly across all of them with the remaining batter.
  
• Get the streusel out of the refrigerator and break it up with a fork, back into those pea-sized lumps.
  
• Spread a little of the topping all over all of the cups, then I go back over to make sure to get it up to the edges. Every loose crumb is worth scooching into a cup!
  

Step 6: Bake

• Make sure the oven has been at desired temperature for at least a half-hour before baking.
• Place both of the pans in the middle of the oven.
• Bake for approximately 27 minutes (25-28). It's easy to over bake these. Don't forget, they'll keep baking in the pans a little when they come out of the oven. I know they're ready by the look of the edges of the muffins, they'll turn a yummy reddish-golden brown.
  
• You'll definitely know they're ready when you poke a toothpick or cake tester into the middle of the middle muffin and it comes out clean.
• Cool for 10 minutes before glazing or serving.
  

Optional: Glazing

• Add the cocount milk and coconut oil to a small bowl or pan.
• Heat it up just enough to melt the oil, but not too hot. I use a microwave to heat up for 30 seconds.
• Crumble in some toasted coconut if you have some, it adds a lovely and surprising extra crunch!
  
• Add the light brown sugar and whisk together until it turns a nice golden color.
  
• Add the wet mixture to the powdered sugar and mix until it gets to a nice consistency. I like it on the thicker side as I find it is still quite runny when warm.
• Drizzle over your muffins and serve!