Line the bottom and sides of a straight-sided 13-by-9-inch metal baking pan with foil.
In a medium bowl, stir together the butter, 3/4 cup of the sugar and the salt. Whisk in the egg yolks. Stir in the flour to make a stiff dough. Transfer about 2 cups of the dough to the prepared pan and press evenly into the bottom. Prick the dough all over with a fork. Refrigerate the pan for 30 minutes (or if short on time, freeze for 5-7 minutes). Preheat the oven to 325 degrees Fahrenheit.
Bake the dough until crust begins to set but does not brown on the edges, about 20 minutes (center will not be firm yet). While crust bakes, prepare the streusel.
With your fingers, combine the remaining sugar with the reserved dough until crumbly. Mixture should hold together when pressed, but readily break into smaller pieces.
Spread the huckleberry preserves evenly over the hot crust. Scatter the streusel over the preserves, careful not to break it up too much. Set oven temperature to 350 degrees Fahrenheit and bake bars near top of oven until top is golden, about 25 minutes. Once cooled, cut bars into 1 3/4 inch squares.