sift the flour, baking soda and salt into a large bowl. Add the butter and mix with an electric mixer on low speed until the largest of the butter pieces are the size of small lima beans.about 20 seconds.
the butter pieces will be different sizes and there will still be some loose flour.
add the sour cream and mix until large clumps of dough form that pull away from the sides of the bowl.about 15 seconds(or use a pastry blender to combine the flour mixture and butter.add the sour cream and stir with a large spoon for about 2 minutes until a smooth dough forms).
form the dough into a smooth ball and flatten it into a rectangle about 8x5".
you will see small pieces of butter in the dough, that is good and contributes to the flaky texture.
wrap in plastic wrap and refrigerator for 30-60 minutes to rest and firm the dough.
the dough can also be refrigerated overnight, but then it will have to sit at room temperature until it is soft enough to roll out easily.
this can take as long as 1 hour in a cool kitchen.
to prepare the FILLING:.
in a large bowl, using an electric mixer on medium speed, beat the almond paste and butter until smooth.
mix in the powdered sugar, cream or milk,vanilla and almond extract until blended to a smooth soft mixture.
OR make the filling in a food processor. Put all the ingredients in the processor, and beginning with a few on/off bursts, process until a smooth mixture forms,.about 1 minute.).
transfer to a small bowl, cover and set aside at room temperature for up to 1 hour or refrigerate if leaving overnight.
position a rack in the middle of the oven.
preheat the oven to 375*.
line two baking sheets with parchment paper.
unwrap the dough.
lightly sprinkle the flour and sugar on the rolling pin and the rolling surface.
roll the dough to a 14x12" rectangle.
don't flip the dough over while rolling, but lift and turn it several times as you roll it to prevent it from sticking to the rolling surface.
and, when you lift and turn the dough, sprinkle sugar generously on the rolling surface.
use a thin metal spatula to spread the filling in a thin layer over the dough.
turn the dough if necessary so a short side faces you.
Measuring along the 14" sides, mark the center of the dough.
rolling from the shorter 12" edge that is closer to you, roll up the dough like a jelly roll just to the marked center.
then roll the far side toward the center until the two rolls meet.
you will have a double log of filled dough that is smoothly attached on the bottom side.
turn the double log over for easier cutting.
press in the ends of the log to smooth them.
and use a large sharp knife to cut the log into 12 1" thick slices.
dip both sides of each slice in sugar, sprinkle the rolling pin with sugar.
roll out each slice of dough to a large butterfly shape about 4x5" and about 1/16" thick, sprinkling the rolling pin as necessary with sugar.
the cookies will not all be exactly the same size.
use a large spatula to place the cookies at least 1" apart on the prepared baking sheets.
sprinkle the top of each cookie with about 1/2 tsp sugar.
bake the cookies one sheet at a time until the tops are evenly light brown.about 15 minutes.
the cookies will spread about 1" and rise slightly.
the filling may bubble up slightly on some of the cookies and have a few darker spots.
cool the cookies for about 5 minutes on the baking sheets.
then use a large metal spatula to transfer them to a wire rack to cool completely.
the outside of the sugar coated cookies will become very crisp as they cool.
the cookies can be stored in a single layer in a tightly covered container at room temperature for up to 3 days.