Warm the milk to 100–110°F in a small bowl, stir in a pinch of the granulated sugar and the active dry yeast, and let stand for 5 minutes until foamy.
In the bowl of a stand mixer, combine the bread flour, remaining granulated sugar, salt, sweetened condensed milk, melted butter, and 1 large egg.
Pour the activated yeast mixture into the flour mixture and stir with a spatula until no dry flour remains. Cover the bowl with plastic wrap and let rest for 20 minutes.
Attach the dough hook to the mixer and knead on low speed, gradually increasing to medium-high, for 10–12 minutes until the dough is smooth, elastic, and slightly sticky.
Lightly oil a large clean bowl, transfer the dough to the bowl, cover with plastic wrap, and let rise in a warm place for about 1 hour, until doubled in size.
Line a 13 x 9 inch baking pan with parchment paper.
Punch down the risen dough to release air, turn it out onto a lightly oiled surface, and divide into 10 equal pieces of about 65 g each.
Shape each piece into a smooth ball by tucking the edges underneath and rolling on the work surface until tight and round.
Arrange the dough balls in the prepared pan, spacing them evenly, cover loosely with plastic wrap, and let rise for 35–45 minutes until nearly doubled.
Preheat the oven to 350°F. Beat the remaining egg in a small bowl for the egg wash.
Gently brush the tops of the risen dough balls with the egg wash and bake for 18 minutes, or until the buns are golden brown on top.
Remove the pan from the oven and let the buns cool completely in the pan on a wire rack.
In a small bowl, dissolve 1 tablespoon granulated sugar in 1 tablespoon boiling water, stirring until clear, then let the sugar syrup cool to room temperature.
In a large chilled mixing bowl fitted with a whisk attachment, combine the heavy cream, vanilla bean paste, powdered sugar, and 1/4 teaspoon salt.
Whip the cream mixture on medium speed until medium-stiff peaks form, then transfer the whipped cream to a piping bag fitted with a 1/2 inch tip or cut opening.
Once the buns are completely cool, use a serrated knife to slice each bun horizontally, stopping about 1/4 inch before cutting all the way through so the bottoms stay attached.
Lightly brush the cut surfaces and tops of each bun with the cooled sugar syrup.
Sprinkle the desiccated coconut over the tops and insides of the buns so it adheres to the syrup.
Gently open each bun and pipe whipped cream generously into the center, using an S-shaped motion to fill the gap.
Serve the coconut cream buns immediately, or cover loosely and hold at cool room temperature for a few hours before serving.