Place all marinade ingredients into a bowl and whisk together; then transfer into a ziplock bag.
Place mushroom caps into the ziplock bag and shake until they are all covered with the marinade. Let the mushrooms marinate for 30 minutes at room temperature or in the refrigerator for several hours.
Once you are ready to grill, heat the grill to medium-high. Place mushrooms, stem side down, directly onto the grill and let cook for five to six minutes. Flip mushrooms and let cook for another two to three minutes.
Remove and let cool, top with goat cheese, tomatoes and chives.