(I'll explain it as a single serviing - you can make as many as you want.)
-Place the portabello in a casserole dish. Lightly spread some butter on the portabello and put it in the over for about 10mins to soften it.
-Cook the chicken breast in a pan with a can of green chiles. Depending on how spicy you want the chicken, you can also season it with red pepper flakes or cilantro
-In a small pot, melt 2-3Tbl of cream cheese, add 1-2Tbl of salsa and keep stirring. The sauce should be a nice salmon color. It should be creamy but spicy.
-Take the portabello out of the oven, have it sitting in the pan stem side up. Place the chicken breast on top. Generously cover the chicken with the cream cheese/salsa mixture. Sprinkle the top with the mexican cheese. Put it back in the oven for approx 10mins to get it melty and hot.