Slice portobello mushrooms into strips and place in a bowl. Toss sliced mushrooms with oil and lightly season with salt & pepper.
Over medium-high heat, pan sear sliced mushrooms until they start getting color. Add 1 packet of Ortega Taco Seasoning (or desired amount) once colored and mix until mushrooms are fully coated. Turn heat down and cook for another 1 minute then take off heat. Set aside.
For the chimichurri, add all ingredients to a bowl and mix. Salt and pepper to desired taste.
To plate, add layer of smashed avocados to a tortilla, add your portobello mushrooms and layer of chimichurri on top.