Combine the ricotta, the sour cream, the remaining egg yolk, the remaining 1 Tbl olive oil, a good pinch of salt and a few grinds of pepper. Mix with a rubber spatula to combine thoroughly. Spread over the prepared puff pastry, keeping within the lines of the scored border. Crumble half of the goat cheese over the ricotta. Arrange the greens evenly over the top, then sprinkle with the remaining goat cheese crumbles. At this point, the tart can be covered with plastic wrap and refrigerated until ready to serve. It can even be made a day ahead. (Always good when it comes to having dinner parties!)
Make the relish: Preheat the oven to 375°F, then toast the pine nuts on a baking sheet, stirring occasionally, until they are lightly golden brown, about 8 minutes.
Heat a small sauté pan over high heat for about 2 minutes, then turn the heat down to medium and add the olive oil, rosemary and chile flakes. Cook for about 1 minute, then turn the heat down to medium-low and add the diced onion. Season with a good pinch of salt. Gently cook the onions for about 5 minutes, until tender and translucent. Add the balsamic vinegar and cook about 5 minutes more. Discard the rosemary and transfer the onions to a small mixing bowl.
While the onions cook, place the currants in a small bowl and cover with very hot water. Let soak 10-15 minutes, then drain well.
Add the currants, toasted pine nuts and parsley to the onion mixture in the mixing bowl. Stir to combine. Taste, then season as needed with salt & pepper.
Finish the tart: Preheat the oven to 400°F. Bake for about 30 minutes, until the crust is golden brown (both on the outside border and underneath – Lift it up a bit to peer beneath and make sure the bottom of the tart is thoroughly cooked too).
Allow the tart to cool for a few minutes, then transfer to a cutting board. Slice the tart. Sprinkle evenly with currant-pine nut relish. Serve right on the cutting board.