Crush biscoff: Place biscoff cookies in a ziploc bag. Smack the cookies with a rolling pin until they're finely crushed. Pour the biscoff crumbs into a small bowl.
Mix crumb mixture: Add shredded coconut and melted butter. Stir until the crumbs are saturated and the mixture resembles wet sand.
Press crust into pan: Transfer the crumb mixture to a 9" fluted tart pan with a removable bottom. Spread them out evenly and use the flat bottom of a measuring cup to firmly press the mixture into a flat layer on the bottom of the pan and up the sides of the pan. Firmly press the crust into all the grooves, removing some from one area and adding it to any thinner areas.
Chill: Chill the crust in the fridge while you make the filling.
Filling
Prep: Preheat oven to 350°F.
Blend mangoes: Add the mango chunks to a blender. Blend until smooth and pureed. Set aside.
Whisk: In a large mixing bowl, whisk the eggs for a few seconds until they're combined. Add the mango puree, condensed milk, salt, and lime juice. Whisk together until combined and smooth.
Fill crust: Pour the filling into the crust. Smooth the top of the filling with a spatula.
Bake: Place the tart pan on top of a baking tray or baking sheet to make it easier to transfer to and from the oven and to catch any excess liquid that may seep out of the tart during baking. Bake tart for 20-25 minutes or until the edges of the filling are set but the middle is still jiggly. Let the tart cool completely on a wire rack before transferring it to the fridge to chill overnight.
Toppings
Whip cream: To a medium bowl, add whipping cream, powdered sugar, and vanilla extract. Use an electric hand mixer or whisk to beat the cream on low-medium speed until it becomes stiff peaks. Transfer the whipped cream to a piping bag fitted with a piping tip of your choice.
Unmold tart: Remove the outer ring of the tart pan by placing the pan on top of a small cup and gently pulling the outer ring downwards. Slide an offset spatula between the tart and the bottom of the pan to release the tart. Transfer the tart to a serving plate.
Mango slices: Arrange the sliced mangoes on top of the tart by gently fanning out the slices in a wavy pattern.
Pipe cream: Pipe squiggles of whipped cream in the empty spaces around the mangoes. Finish with a sprinkle of lime zest over the whole tart.