I have never owned a double boiler, nor a steamer. So perfect vegetables were a dream unless I microwaved them and I am all pro-microwaving, just that this one time it was occupied and I had just bought these sugar snap peas and had an intense craving to crack open the sweet subtlety, right away. Of course I was not going to boil them.
I quarter filled a small pot with water, I placed a rice sieve snugly on top.
(Mom had bought me this strainer when I first moved out and I hadnt given it much use beyond the occasional pasta dripping).
Simple principle: Boiling water will create steam to cook the veggies but no water will touch the veggies, so they’ll be soft but not mush and above all cleaned, but not washed out.