For the sweet pastry: Add flour, butter, sugar and salt to the bowl of a food processor and whirl until the mixture resembles coarse crumbs. Separate the egg; place egg yolk in one small bowl and egg white in another small bowl. Reserve the egg white for brushing the top of tarts. Add egg yolk and cream cheese to the food processor and pulse until combined and the dough starts to clump together.

Divide dough into 2 portions and shape each into a disk. Wrap each one tightly in plastic wrap and refrigerate for 1 – 2 hours until firm.

Meanwhile, make the apple cranberry filling: In a medium-sized saucepan whisk the lemon zest, lemon juice, ¼ cup water, sugar, cinnamon and cornstarch. Add apples and cranberries and cook over medium heat for 4 – 6 minutes (longer if using frozen cranberries), while stirring occasionally, until most of the cranberries burst and the apples soften. Add up to ¼ cup more water, a little at a time, if necessary.

Break up apple pieces and any un-burst cranberries with a fork to achieve a lumpy consistency. Continuing cooking for 2 - 3 minutes until the mixture thickens slightly. Remove from heat, transfer to a bowl and refrigerate to cool, at least 1 hour or longer. The filling will thicken as it cools.

Preheat oven to 375 degrees F. Prepare two 24 cup mini muffin pans.

Roll out the sweet pastry: Working with one disk of dough at a time, on a lightly floured work surface roll dough into a 14” circle (about ⅛” to ¼” thick). Cut out 30 three-inch circles, re-rolling the scraps from each disk as necessary. Place the circles into the cavities of the muffin pans by gently pressing them into the bottom and up the sides, bringing the edges of the dough to just above the rims. Wrap and refrigerate remaining scraps for the heart cut-outs.

Fill each pastry cup with about 2 teaspoons apple cranberry filling. Place the pans in refrigerator to keep the tarts chilled for at least 10 minutes while cutting out the hearts.

Re-roll remaining scraps to ⅛” - ¼” thickness. With a small heart shaped cookie cutter, cut out 30 hearts. Place a heart cut-out on top each tart, do not press. Lightly whisk the reserved egg white. Brush the heart and exposed pastry edges with the egg white and sprinkle with coarse sugar crystals.  

Bake for 20 - 22 minutes until golden brown. Let tarts set in the pans for 10 minutes before removing to a rack to cool completely. Store in refrigerator and serve cold or at room temperature.