Stuffed Tomatoes

This is not the 'tuna stuffed' tomato that I grew up having.  I do love tuna stuffed tomatoes, but this is out of this world good.  I also love that it's vegetarian.  They are only 185 calories each.

STUFFED TOMATOES
(serves 4)

Ingredients:
*4 large tomatoes
*1 (10 ounce) container chopped frozen spinach, thawed
*1/2 cup mushrooms, chopped
*3/4 cup chicken stock (or vegetable stock)
*2 garlic cloves, minced
*1/4 teaspoon dried thyme
*1/2 teaspoon italian seasoning
*1 tablespoon, freshly squeezed lemon juice
*1/4 cup fresh ricotta cheese
*1/2 cup freshly grated parmesan cheese
*a pinch nutmeg
*1 egg yolk
*1/2 teaspoon salt
*1/2 teaspoon black pepper
Optional
*1/4 teaspoon spicy brown mustard
*1 tablespoon white wine vinegar
*3 teaspoons olive oil
*1 teaspoon dried basil

Directions:
~Bring a large pot of water to a boil.
~Carefully drop tomatoes into boiling water for 1 minutes.
~Remove from water and put into a large bowl of ice water.
~Squeeze liquid from spinach.
~In a large saucepan, spray a cooking spray into the bottom of a large sauté pan.
~Sauté mushrooms, over medium-high heat, until they begin to brown.
~Add chicken/vegetable stock to the mushrooms.
~Reduce heat to medium.
~Add minced garlic, thyme, italian seasoning & lemon juice.
~Cook until all the liquid has evaporated.
~Remove from heat, and cool.
~In a medium bowl, mix ricotta cheese, parmesan cheese, mushroom mixture, spinach & egg yolk together.
~Mix in salt, pepper, thyme & italian seasoning.
~Preheat oven to 325 degrees.
~Peel tomatoes & slice off the tops.
~Carefully scoop the pulp out of the tomatoes into a small bowl.
~Set pulp aside.
~Carefully stuff the tomatoes with the cheese-mushroom mixture.
~Place place stuffed tomatoes into an oven proof baking pan.
~Drizzle with a small amount of olive oil.
~Bake for 30 minutes.
~While the tomatoes are cooking, whisk spicy brown mustard, vinegar, olive oil & basil into a small bowl.
~Remove tomatoes from oven when done, drizzle mustard mixture over the tomatoes & serve.