Whisk together all filling ingredients, cover and set aside.
Preheat oven to 350 degrees.
Combine dough ingredients together, either in a standing mixer using the dough hook, or kneading by hand, and continue the kneading for five minutes.
Divide the dough into equal halves.
With the surface very floured, roll half of the dough out into a 1/8" thick rectangular slab, that is 12" long by 22" inches wide.
Using a ruler or tape measurer, measure out and score the outer border of a large rectangle in the slab that measures 18 inches wide, by 8 inches long. Then, measure, score and cut 12 rectangles in total within the large rectangle. These will be two rows of 6 rectangles, each 3 inches wide by 4 inches long. Pull back the excess dough and set aside.
Using a spatula, transfer rectangles to a parchment lined baking sheet; these will be the bottoms of the toaster pastries. Keep an inch or so of room in between each one.
Fill the centers of each rectangle with one heaping tablespoon of the filling mixture, spreading it longways, and leaving the outer quarter inch of pastry dough dry.
Repeat the dough rolling, and rectangle cutting process on the other half of the dough. Again, keep the surface and rolling pin generously floured.
Lay the top rectangles right over the filling on the bottoms. Use the tines of a fork to press all the way around each pastry to completely seal the two pieces together.
Use a toothpick to poke several holes into the top layer, being careful not to pass past the filling into the bottom layer.
Bake in a 350 degree oven for 14-18 minutes, until edges are cooked and centers are set. Check periodically towards the end, and avoid letting the pastry tops crack. Cool on a wire rack.
Prepare icing. Sift powdered sugar first, if necessary, and whisk with icing ingredients. The turmeric is optional, as it is just for color. Spread onto completely cooled toaster pastries. Sprinkle with additional cinnamon, if desired. Icing will set within 15 minutes.
Store at room temperature, covered for up to four days, or freeze extra batches.
To heat, toast on the lightest setting, or microwave for 20 seconds. Filling will be hot!