Place the flour in a medium bowl. Add the butter and cut it into the flour using a fork or your fingers until mixture resembles coarse meal.

Gradually fold the sour cream into the flour mixture, until a soft dough forms. 

Remove the dough from the bowl, form into a thick disc and wrap in plastic wrap. Place in the refrigerator overnight.

Remove dough from the refrigerator and let it warm up on the counter before rolling - about 20 to 30 minutes.

Preheat oven to 350° and line a rimmed baking sheet with parchment paper. 

On a lightly floured surface, roll the dough into a thin round circle - about 18” in diameter, and about ⅛” thick (if it cracks a bit, that’s ok, it will be covered when you make the roll).

Spread the apricot preserves (or preserve of your choice) in a thin layer over the entire surface of the dough circle.

Evenly sprinkle the sugar, cinnamon, coconut, and walnuts over the layer of preserves.

Starting at the bottom edge of the dough circle, carefully roll into one large log. Cut the log into four, equal sized bars. Score the top of each bar with 3-4 diagonal slashes to allow for steam to release.

Place the 4 bars on the prepared baking sheet and bake for 35 minutes until the crust is golden brown, rotating the pan halfway through for even baking.

Remove from the oven and let cool. As Aunt Blanche would say, “when you are ready to serve, slice them on the "bias" and gently sprinkle with powdered sugar”.