Pulse together flour, salt and baking powder in a food processor for about 10 seconds to evenly combine the ingredients.
Cut cold butter into 1/2" chunks and add to the food processor. Pulse until mixtures resemble breadcrumbs, about 30 seconds.
Add yogurt and pulse until dough comes together into a ball, about 10 seconds. Do not over mix. Dough will be sticky.
Turn dough out onto a well floured surface, cut in fours and form each piece into a disc. Wrap well and refrigerate for 1 hour or overnight. At this point the dough can be frozen to use at a later date. Thaw in the refrigerator for 24 hours hours before proceeding.
To prepare filling, toast chopped nuts on a parchment lined baking sheet in the oven for 5 minutes at 400˚F.
Cool nuts at room temperature and mix with brown sugar and cinnamon. The nut mixture can be made ahead of time and stored in an airtight bag or container at room temperature until ready to use.
Take one disc of dough out of the refrigerator and roll it to a 1/4" thick round about 9 1/2" in diameter on a well floured surface. Dust dough, rolling pin and surface with more flour as needed to keep dough from sticking.
Spread 1/4 of the jam in a layer over the surface of the dough. Then sprinkle 1/4 of the nut mixture all over the jam.
Cut dough into 12 wedges with a sharp knife or pizza wheel. First cut dough in half then in quarters, then cut each quart section into thirds.
Use an offset spatula to gently pull a wedge out of the circle and then roll it up from the outer edge to the point. Transfer to a parchment lined half baking sheet with seam side down.
Repeat steps 8-11 with the second disc of dough.
Brush the tops of pastry with non-dairy milk and sprinkle with granulated sugar.
Bake the first two sheets on the bottom and top third oven racks at 400˚F for about 20-25 minutes until pastry is golden brown. Turn sheets halfway through baking. The filling will ooze out a little during baking.
While the first 2 sheets of cookies are baking, prepare the next 2 sheets by repeating steps 8-14.
Allow cookies to cool on sheets for 1 minute before transferring them to cooling racks to cool to room temperature.
Store cookies in covered containers or bags for up to 1 week at room temperature or freeze for up to 6 months. If frozen, thaw in the fridge then warm them back up in the oven before serving.
Use thick non-dairy yogurt such as Coyo coconut yogurt or strain liquid from a runnier yogurt through a coffee filter or nut-milk cloth set in a strainer over a bowl to thicken it. Discard the liquid that collects in the bowl and use the thickened yogurt in the coffee filter/cloth.
The thicker the jam the better as it tends to ooze out during baking. I found that the fig jam I used worked best, while apricot preserves were more runny.
Recipe by Fare Isle at https://fareisle.com/vegan-rugelach/