Process pecans, vanilla bean and sea salt in food processor until mixed well. Add 3/4 cup dates and continue to process until well mixed.
Transfer half of the mixture to a pie dish and press with a wooden spoon or spatula. Set aside the remainder of crumbs for the topping.
To process the syrup, place 3/4 cup dates, oil and vanilla bean in processor and blend well. Slowly add water to give the mixture a syrup-like consistency.
Place mangoes into a large bowl and toss with the syrup. Transfer the mangos into the pie dish and spread evenly. Top with the remaining crust mixture and serve.
This dessert will keep for 2-3 days in the refrigerator.