Prepare Yumbini with 3/4 cup water according to package directions.
Unless your mushrooms are VERY dirty, do not wash them with water! Clean them gently with a towel. This prevents the stuffed mushrooms from being too watery.
Pop the stems off the mushrooms and place the tops on a cookie sheet lined with parchment paper. (Hint: you can skip the parchment paper if you don't have any.)
Chop the mushroom stems finely (about 1/2-1/4").
Chop the carrot as finely as possible (1/8-1/4"). Remove cilantro stems and chop the leaves coarsely.
Heat the oil in a stainless, carbon steel or cast iron skillet. Add chopped mushroom stems and carrot. Sautee until most of the water is out of the mushrooms and the mixture is starting to brown. Turn off the heat.
Add prepared Yumbini, cilantro and cheese and mix well.
Preheat oven to 400F.
Fill Yumbini mixture into the mushroom tops. Mound up on top and press down into the cavity. (Hint: go ahead and ditch the spoon and fill using your fingers!)
Bake about 15 minutes at 400F, until moisture is starting to collect under the mushrooms. Cool slightly before serving.
Enjoy as an appetizer or all-out dinner!