The bitterness is likely a matter of using far too much, and may also relate to your source of supply, the form you're using.
Portion control is difficult.
I use both extract and the raw form for nearly everything I do these days, including baking of biscotti, etc. If this is the form you're using, and you're experiencing bitterness, I suspect you need to use far less. The green, or 'raw form' has a slightly 'minty taste' and I'm quickly becoming quite fond of it in herbal teas. I think I learned that it's grown in many places, and that the taste can vary some.