1. Make sure the rack in your oven is in the middle. Preheat to 400°F.
2. In a medium skillet over medium heat, add oil and onions and cook the onions until very soft and a deep golden brown, takes about 10-15 minutes, adjust heat so they don’t turn dark brown or burn.
3. You’ll need a large rimmed baking sheet. The puff pastry comes rolled up in a sheet of paper, unroll it. Place a piece of parchment paper on top and the flip it over. Place this on the baking sheet and then peel off the paper the puff pastry came in.
4. Using a fork, poke tiny holes all over the pastry. Using your fingers crumble the goat cheese all over the top of the pastry. Set aside until the onions are cooked.
5. Once the onions are cooked add apple, maple syrup and pepper and sauté for 2 minutes or until the apple starts to soften.
6. Here comes the tricky part, carefully spoon out the onion/apple mixture evenly over the goat cheese, making sure you have great distribution of both onions and apple. Bake for 25-30 minutes or until the pastry is cooked through and the edges are golden brown.
7. Remove from oven and evenly sprinkle the walnuts over top. Pick up the tartlet by holding onto the parchment paper and place on a cutting board. Cut into 16 pieces and serve right away.
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