Preheat oven to 400°F. Line a baking sheet with parchment paper. Roll out the pastry and place it on the lined baking sheet. Cut into 4 sections. Using a sharp knife, score the pastry, about 1 inch (2.5 cm) in from the edge. Then fold over about half the measurement to create a height on the edges. If you prefer, you can leave the edges scored without folding. Brush with egg wash over the edges and center of the tarts, then poke holes with a fork. Bake for 10-12 minutes until it’s lightly golden. Remove and set aside to cool.
In a large skillet, over medium heat, add 2 tablespoons of olive oil and then add leeks and sauté for 6-8 minutes until softened and starts to caramelize, a golden colour. Add garlic for the last 30 minutes, long enough to release the aroma. Set aside.
In a medium bowl, add the tomatoes, olive oil, balsamic vinegar, basil, salt and pepper. Stir to combine and set aside.
Spread the caramelized leek and garlic over each tart section. Add large dollops of goat cheese and then gently press the tomatoes into the cheese, and drizzle any remaining olive oil and balsamic vinegar mixture left in the bowl over each tart section.
Bake until the pastry has risen, turned golden brown, and the tomatoes are softened and started to burst, for approximately 25 minutes.
Remove from the oven and if you prefer you can drizzle some more olive oil and balsamic vinegar over each tart. Garnish with parsley. Serve with arugula or salad.