Add the tomatillos, chopped onion, garlic, Serrano pepper, cilantro, chicken bouillon granules, water, sugar, and salt to a blender. Blend for 1 to 2 minutes or until smooth. In 1-quart saucepan, heat 1 teaspoon canola over medium-high heat. Add the tomatillo mixture and cook, stirring occasionally, for 3 to 5 minutes or until the salsa turns to a deeper green. Set aside. In a small bowl, mix the sour cream and milk, stirring constantly for 1 or 2 minutes. Set aside. Brush the meat with the remaining oil and rub with kosher salt. Thread the meat, bacon, green and red peppers alternately, and quartered onion sections onto the 4 skewers leaving a small space between each item. Grill on medium-high heat for 8 minutes or until the meat is cooked to desired doneness and the vegetables are slightly charred, turning the skewers around occasionally. Remove the meat and vegetables from each skewer. Place on the tortillas and top with cheese and a slice of avocado. Drizzle with sour cream sauce. Serve with Pico de Gallo if desired.