Combine the chiles, tomatillos and 3 cups of water in a medium saucepan. Bring to a boil, cover, and cook until the tomatillos are soft, stirring occasionally, about 10 minutes. Drain and let cool.
In a food processor, combine the chiles, garlic, salt, aniseed and oregano. Blend until smooth. Strain the mixture through a fine mesh sieve, discarding the solids. Wipe the saucepan clean and add the olive oil. Heat over medium-high heat, then add the strained sauce. Simmer for 5 minutes, then add 1 cup of water. Bring to a boil. Once boiling, add the steak and reduce the heat to medium-low. Cook until the sauce lightly coats the back of a spoon, about 15 minutes. Taste and add more salt, if needed.
Scoop the flesh from the avocados and place in a medium bowl. Mash roughly with a for. Add the cilantro, onion, lime juice and salt. Mix.
Place 2 tablespoons of the guacamole down the center of each tortilla. Roll up and place on a plate, seam side down. Pour the warm meat sauce over the tacos, and top with additional cilantro and crumbled queso fresco.