In a bowl mix the flour, baking powder, salt, and sugar (if using). Add the butter cubes and work the flour into the butter with your hands. Flatten each chunk of butter between your thumb and forefinger. Add the sour cream and mix to moisten the dry ingredients with the sour cream. Knead the dough together adding ice water by the teaspoon only if necessary for the dough to hold together. Place the dough onto a sheet of plastic wrap, and press into a disk as you close the plastic wrap around the dough. Place the dough in the refrigerator to chill for 30 minutes.
To make the strawberry jam
In a saucepan, add the strawberries, Maple Syrup, Vanilla Extract, Lemon Juice, and Lemon Zest. Let it simmer over medium heat, stirring frequently mashing the strawberries as you stir. After 5min, mix the corn starch with the water (aside) and then add it to the saucepan. Continue stirring frequently. Cook for another 5min, or until the spread starts to thicken. When it is done, remove it from the heat and let it cool down for 5min.
To make the pop tarts
When you have your pie dough ready. Dust your work surface lightly with flour. Remove one portion of dough from the refrigerator and let sit for 5-10 minutes to soften. Carefully roll into a 9x12-inch rectangle, dusting with flour and flipping to keep it from sticking. Repair any cracks as you roll. Cut your desired pop tart shapes, you can do the regular rectangle shapes or use a cookie cutter like I did and cut them in heart shapes.
Brush egg over the entire surface on one side of a cut-out shape doug and place 1 teaspoon chilled lactose-free cream cheese and 1 teaspoon strawberry jam in the middle. Carefully place a second cut-out shape on top and press the edges to seal, being careful not to press the jam out of the sides. Use the tines of a fork to crimp the edges.
Repeat with remaining cut-out shapes, laying each on a parchment-lined baking sheet about 1-inch apart.
Use the end of a chopstick or thick skewer to poke a few holes in the top of the pastry to vent out the steam. Chill the pop tarts for 15 minutes while you preheat the oven to 200°C or (400°F). When the oven is done preheating, brush the top of each pop tart with the remaining egg wash.
Bake for about 20 minutes or until the tops are golden brown and crisp. Remove from heat and using a clean cloth, paper towel, or flat spatula, gently press the pop tarts down to remove any steam and flatten them a bit. Let cool completely before icing.
To make the icing
Simply mix the cream cheese with the strawberry jam
Put 1 teaspoons of glaze on a pop tart and use a spoon to gently spread it around. Top with sprinkles and repeat with remaining pop tarts.