"Vegan sour cream is easy" it what this recipe says. Okay. It might be easy, but this doesn't mean tasty.
I tried to blend firm tofu into a creamy texture before and I never was satisfied with the result. I just found this recipe and wanted to try it with silken tofu but as I only had firm tofu at home and didn't wanted to go shopping, so I tried it with what I had at home and afterwards I actually think, with silken tofu this will be more a dip or a sauce than something like sour cream.
I had to adjust the recipe and am really confused about the measurements. The "package of tofu" which is used in this recipe contains almost 400g tofu (see in the comments), I had a package with 200g. But I had to use way more liquid, as in the recipe. Maybe it varies from brand to brand so you might have to experiment a bit, too.
The result is quite alright - creamy and fluffy, better than I expected. The taste is also quite alright, but the cream is still a tiny bit floury. This distinctive feeling on your tongue which comes from the tofu.
So, yes, it tastes like tofu/soy. I you don't like that, just don't do this at home!
All in all it also has this lightly fresh, sour-ish taste you want from sour cream and in combination with fresh cut veggies or as an addition for your home-made burrito it's worth a shot. I prefer the version with cashew nuts (tons of recipes online) but this is a good and less expensive alternative.
Here's my slightly altered variation:
2 tbsp olive oil
3 tbsp lemon juice
2 tsp soy sauce
splash of water if needed
I started without the water and added it near the end and then it was finally really creamy. I recommend a food processor as a handheld blender might not work.
Make sure to let chill in the fridge for 30min or more.