This afternoon I made two cups of Whittard of Chelsea blackcurrant and blueberry tea, which was sent to me as an unexpected gift by a friend from London. They are so strong that I was able to make a second cup, which also tasted great. While brew is the correct term, we would rarely use it in reality. We generally prefer simple verbs like do and make, unless it is some kind of technical writing. Also, try to avoid repetition - use ether unexpected or surprise, but not both. Your sentences were perfectly correct and understandable, but they don't sound very natural because they are a bit 'wordy'. Try to make your sentences simpler by changing the order of adjectives so you don't need to use 'of', for example. And you don't need to say you drank it for a second time - we know you must have done if you knew that it tasted great.

"This afternoon I brewed two cups of tea, blackcurrant and blueberry, by Whittard of Chelsea. It was an unexpected surprise gift that a friend in London sent me! Because the flavor is SO strong, I brewed it twice, and the second time I drank it, it still tasted great." I'm not sure what you mean when you say you "brewed it twice". Do you mean to say that you used the same tea bag a second time, or did you start the second time with fresh tea? The distinction is important because the logic of the sentence is difficult to understand. Why should it be a surprise that it tasted great the second time? In my opinion, "brewed" is a good verb to use. Here where I live, the word is used commonly.

As I understand it, it might not taste as good the second time, due to some of the flavor being gone. Either 'in' or 'from' would leave some ambiguity. 'From' does sound more like he was born and raised there; however, he may have left London and now be living somewhere else. Fortunately almost all places have a term for someone from there -- you could also call him a Londoner. Or you could call him your English friend in London.