Mix the flour, salt and yeast in a medium size bowl.
Add and toss the cut butter cubes until fully coated. Use a pastry blender to cut in the butter until mixture reassembles a coarse meal.
Scant sour cream to the flour mixture and stir with a fork until fully incorporated. Use your hands to quickly gather together a shaggy mass until it holds together. Don’t overwork it!
Put the dough into a large Ziploc bag, pressing out the air or wrap it tightly in a plastic wrap. Flatten the dough in a rectangular or disk shape and refrigerate, minimally 4 hours and ideally overnight.
Filling
Whisk the cinnamon and sugar together in a small bowl and divide into 4 equal portions.
Chop the walnuts very finely and divide into 4 equal portions.
Assembly
Preheat the oven to 190 °C (375 °F).
Divide the dough into 4 equal pieces. Leave one dough piece out and wrap individually each of other 3 pieces, put them back to the fridge.
Using your hands, shape the dough into a flat disk. Sprinkle with one portion of cinnamon/sugar mix and roll out to 38 cm (15″) circle. Frequently flip over the stretched dough and sprinkle with the mix. Make sure that all of the cinnamon/sugar mix portion is used.
Sprinkle the stretched dough with one portion of chopped walnuts. Spread the walnuts as evenly as you can and press them down lightly.
Using a pizza cutter or knife, cut the dough circle into 16 wedges.
Starting from the base of the each wedge, roll the dough towards the tip or the center of the circle and form a small crescent roll.
Place all 16 crescent rolls on a parchment paper lined baking sheet. Place each roll so the tip of the rolled wedge is at the bottom.
This will prevent the rolls from uncoiling during baking.
Bake for 18-20 minutes until the crescent rolls are golden.
Repeat the same process with the other 3 dough portions.