In a medium saucepan, cook the soba noodles in boiling water, as directed on the package.
Meanwhile, make the dressing: Put the tahini paste, miso paste, rice vinegar and Sriracha in a large bowl. Whisk well.
Drain the cooked noodles and rinse under cold running water; set aside in the colander. To keep your noodles from clumping together, rub them together when rinsing to wash away excess starch. This will also make sure they maintain a perfect texture.
Add the drained and cooled soba noodles to the dressing bowl and toss. Add the jicama and baby spinach; mix well.
Top the noodles with avocado slices and gomashio. To serve, twirl the noodles using tongs and place in individual serving bowls.