Combine water, salt and rolled oats in a large sauce pan over high heat. Bring to a boil. Once boiling, turn down the heat enough so you don’t have a boil-over and let simmer for about 20 minutes, or until oatmeal is cooked. Once oatmeal has finished cooking, stir in miso. Leave oatmeal in the pan on the burner but turn the heat down as low as possible.
While oatmeal is cooking, prepare bacon. Place bacon slices in a medium nonstick sauté pan over medium heat. Cook until fairly crisp, flipping once. Remove from pan and set on a small plate lined with a paper towel. Reserve bacon grease in pan.
Using the pan you cooked the bacon in that still has the grease in it, sauté your leeks. Continue cooking the leeks, stirring occasionally, until they are tender and have taken on a slight golden hue.
Add sautéed leeks to oatmeal, stir to combine. Chop up bacon into small pieces, and add that to the oatmeal as well, stirring in until combined.
Now, cook your egg. This is where you can be flexible. I recommend preparing the eggs in whichever style is your favorite! Of course, the over-easy egg is great because of the runny yolk, but if that’s not your thing, feel free to scramble or fry.
Spoon oatmeal into individual serving bowls, then top with walnuts, avocado and tomato. Lastly, add the egg. Serve immediately.