Hi
I've been learning how to brew perfectly in the past two years
there are three things that you need to get right
1. Grind , the perfect grind size is to be in between a coarse grind for french press and and espresso grind
2. Ratio, thumbs of rule is 15g of grinded beans and multiply that by 14/15 for the total water (in grams)
3. Length of brew, no matter how much you brew, the total brew time should only last 2-3 minutes, longer than that it will over extract. This has a direct relation with your grind size, if you make for 2 that means you have to use 30g of beans and you want your grind to be a bit coarser than the 15g batch so the brew will be within 2-3 minutes (since more beans for the water to go through during pouring)
other things
- a good scale is very helpful
- keep your water temp to be around 94c-96c (perfect temp)
- try to use medium roast beans