Butterfly your pork tenderloin (lengthwise down the middle)
Mix together all ingredients except mushrooms and lemon to make a sauce.
Drizzle with olive oil, salt and pepper as desired.
Add a row of mushrooms
Using cooking twine close the tenderloin
Place in deep dish pan
Pour sauce over meat
Squeeze fresh lemon over meat or add a layer of lemon slices on top
Bake at 350°F until the meat's internal temperature is 160° (making sure the probe is in the meat and not sitting in with the mushrooms)
Approximate cook time should be about 30 to 45 minutes.
Use the extra sauce at bottom of pan for dipping!