Preheat the oven to 300 degrees F. Line the bottom and sides of an 8-inch square baking pan with parchment paper, leaving enough overhang on all sides. Set aside.
To Make the Shortbread Crust:
In a medium mixing bowl, stir the melted butter, Zing baking blend, vanilla, almond and salt together. Add the flour and stir until everything is combined. Mixture will be the consistency of wet sand. Using the back of a rubber spatula, press the shortbread mixture into the bottom of prepared baking pan in an even layer.
Bake for 15 minutes.
Remove the crust from the oven, and increase the oven temperature to 350 degrees F.
Spread preserves evenly over warm crust.
To Make the Streusel Topping:
In a mixing bowl stir the oats, brown sugar, Zing, cinnamon, and flour together.
Using a food processor, pastry cutter, two forks or your hands, work the cold butter into the mixture. Mixture should look like very coarse crumbs.
Sprinkle the streusel topping over the raspberry preserves in an even layer.
Bake for 30 minutes, until the preserves are bubbly and the streusel is golden.
Let pan cool at room temperature for 20-30 minutes, then refrigerate for several hours to completely set.
Carefully use the overhang of parchment paper to lift the bars out of the pan and slice into desired number of bars.
If desired, drizzle bars with melted milk chocolate (see notes section below).
Garnish with fresh raspberries and/or sliced almonds if desired.