I have tried unsuccessfully to make miso soup before but all I did was add miso to water. Though this will give you a simplified version you probably won’t find the flavour you are looking for.
Your basic ratios are 1 cup of dashi to 1 teaspoon of miso. Dashi is the stock or broth used to make the soup. In the dashi the ratio is 1C water to 1 tablespoon of bonito flakes and 1 tablespoon of kombu. You will also want green onions for garnish.
4t miso
4T bonito flakes
4T kombu
1 green onions sliced, dark green part only
soy sauce if desired
1. Put 4 cups (1qt) cold water in a pot. Add the kombu and bring to just before a boil. you want to remove the kombu before the water comes to a boil – do not discard but save it.
2. Bring the water to a boil and then add another cup of cold water to reduce the temperature of the water down.
3. Add the bonito flakes and bring to a boil. As soon as the water has boiled remove from the heat and strain out the bonito and skim if necessary. At this point you have Dashi.
4. Return the Dashi to the heat on medium and add the reserved kombu. In a glass measuring cup put your miso and dissolve in some of the Dashi. (I cheated and used a whisk.) Add the miso to the soup.
5. Bring the soup up to a simmer and serve garnished with green onions.
A couple of notes – I like my green onion a little softer so I put them right in before I bring the soup up to a simmer in step 5. Also you can buy pre-made dashi – so you could skip steps 1-3 but it does really only take 10 minutes.
I was able to get all these ingredients at this great little place near me in Vancouver, email me if you are interested. I would suggest trying an Asian supermarket near you. Since I live in Vancouver I may be in slight denial about how accessible these things are in other places 
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I put miso paste in a large cup and add hot water from a cooler. Stir vigorously until melted. You can add some green onions if you like or small bits of tofu and then microwave it for 45 sec until it slightly bubbles. It’s like having hot chocolate and it’s perfect for a quick hot drink. My daughter and I love it.
Really? I used to try and make it that way but always found it a little bland – maybe you have access to better Miso then I do! It is great comfort food either way.
I make dashi almost daily and find the cold water method (mizudashi) really convenient, especially since I love having miso soup for breakfast so it cuts down the time of making fresh broth.
Simply soak the kombu and bonito overnight. I do tend to use more bonito and kombu than you mentioned however (a handful of bonito and a 4″ strip of kombu for 4 cups water). Sometimes I’ll switch it up and throw some dried shiitake in instead of bonito.
I think a good point to mention is make sure the heat never exceeds a simmer once the miso has been added or else all the good natural digestive enzymes present are destroyed.
This thread is pretty old… but I’m willing to bet the store you speak of here in Vancouver is Fujiya… I love Fujiya.
Christopher – this is great information, I have never heard of mizudashi and I will defintley try it. Also a great point about not boiling the miso, I have don it accidentally and it also changes the flavour.
I was actually talking about T&T, but when I love in Victoria I went to Fujiya regularly. T&T is just more convenient