Instructions

The Day Before

The Pastry

1. Mix the flour, sugar, and salt together in a ceramic or glass bowl.
2. Add the sourdough starter and melted butter. Mix everything until just combined.
3. Cover the bowl and let the dough ferment at room temperature for 4-5 hours.
4. Divide the dough in half and shape each half into a round disk. Wrap each disk and refrigerate for at least 12 or up to 48 hours. Note that the dough will get more sour the longer it ferments.

The Filling

1. Place the blackberries and water in a small saucepan. Cook over medium heat, stirring often, until thickened and jammy.
2. Add the fresh sage and honey and cook a little longer.
3. Remove the filling to a glass container to cool. Cover and refrigerate the filling overnight.

The Next Morning

1. Remove the dough from the refrigerator and let it soften slightly at room temperature, about 30 minutes to an hour.
2. Preheat your oven to 375°.
3. Cut three large sheets of parchment paper.
4. On a large open work surface lightly dust one sheet of parchment paper with flour.
   Roll the dough into a loose rectangle.
5. To make a really tight rectangle use the parchment to fold the edges of the dough up and over.
6. Continue to roll the dough gently, forming a nearly perfect rectangle about 1/8 inch thick.
7. Using the parchment as a sling move the rolled dough aside and repeat steps 4 to 7 with the second dough ball.

Optional Decorative Steps

1. Place 12 evenly spaced sage leaves on the dough. Cover the dough with the third piece of parchment and roll the leaves into the dough.
2. Flip the dough over so the leaves are on the bottom and remove the parchment paper from the upward-facing side.
3. Set the sage pastry aside.
   

Filling The Pastries

1. Working with the original pastry rectangle, envision 12 equal pastry spaces. Place one heaping tablespoon of jam in the middle of each pastry space.
2. Carefully, and using the parchment as a sling, line up the edges and flip the second pastry over the first. This should reveal the sage leaves on top. Gently but firmly press down around each filling bubble to squeeze out any air.
3. With a knife or pizza cutter, trim the edges of the pastry to make a smooth outer edge.
4. Cut the pastries between each bubble of filling, making 12 even squares.
5. Working with one square at a time, crimp the edges with a fork.
6. Place the tarts on a parchment-lined (use the paper you already cut) baking sheet with plenty of room around each tart.
7. Bake the tarts for 15 minutes or until golden brown.
8. Remove the tarts from the oven and cool them on wire racks.
9. The tarts can be served warm with drizzled honey, ice cream, or whipped cream.
10. Cool completely on wire racks before freezing.