Bring quinoa, stock(in place of water), chiles and sauce to a boil in a saucepan. Reduce heat to low, cover and simmer until quinoa is tender, and stock has been absorbed; about 10 to 20 minutes (depending upon package instructions). Stir and set aside uncovered to cool.
While quinoa cooks, saute garlic and chopped leek with 1 tablespoon oil in a skillet on medium-high heat for 3 minutes. Add beans. Cook for 3 minutes; stirring occasionally. Mix in sage and remove skillet from heat and set aside to cool.
Place half avocado chunks in a small bowl and mash. Add mayonnaise, yogurt, cilantro, lime juice, zest and remaining oil; mix to combine. In a large bowl, add black bean mixture, quinoa, avocado mixture and tomato. Toss to combine. Fold in remaining avocado. Spoon into warm tortillas and sprinkle with shredded cheese. Serve.