Place chicken, ranch dressing mix, pepperoncini, pepper juice, butter, and water, in that order, into a slow cooker. Cook on High for 2 hours or Low for 3 ½ hours until chicken easily shreds with a fork.
Preheat the oven to 350 degrees F (1 degreesC). Remove half of the liquid in the slow cooker and discard. Shred chicken in the remaining liquid. Stir in cream cheese and sour cream.
Place about ½ cup chicken mixture and 2 tablespoons cheese in each tortilla and roll to seal. Place seam side down in a 9x13-inch casserole dish. Top with remaining cheese and pour heavy cream evenly over the top.
Bake in the preheated oven until browned around the edges and bubbly, about 30 minutes. Let stand for 5 to 10 minutes before serving. Top with green onions and pico de gallo.
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