Stuffed Portobello Mushrooms

I recently became starkly aware that I haven't updated to this in quite some time, which is a darn shame, because some pretty neat things have been happening in my kitchen lately.
So this is the stuffed Portobello. It's a recent concoction, and totally delicious.
I keep reading and hearing all these benefits to going vegetarian, but the reality is that I can't, because bacon and beef are both things. So, I will be a meatasaurus until the end of my days.
That said, this dish can easily convince me to make a higher percentage of my meals vegetarian.

Ingredients:
4 to 8 large Portobello mushrooms, depending on their size
1 cup diced yellow tomato
1 cup diced red tomato
1 cup shredded mozzarella
1 cup Panko breadcrumbs
1/2 cup chopped chives
salt and fresh ground black pepper, to taste

Directions:
Preheat broiler.
Remove mushroom stems.
Clean gills out of inside of mushroom.
Cover a baking sheet with aluminum foil and coat lightly with olive oil.
Broil mushrooms, gill side down, for five minutes.
Combine tomatoes, cheese, Panko, and chives in a large bowl and mix well.
Stuff mushrooms with filling, and broil for five minutes, or until cheese is melted.
Serve with light salad, or as a side dish.

Notes:
The gills are kind of a pain to get out of the mushrooms and spooning them out can result in tearing into the flesh, so try to be as gentle as possible.
The mushrooms shrink a LOT in the oven, so account for that when you purchase them. We only bought four and ended up with a lot of stuffing left over. Thankfully, it worked super well in pizza several days later!
If you've never had them before, you should know that yellow tomatoes are really quite sweet. I didn't know this ahead of time, as I'm not much of a tomato person, so I was taken back by the flavour. I think it throws the dish off a bit, so I would probably give them a soak in something savory next time to counteract it, but the sweetness is not a deal breaker, by any means.