How to Make It
In the bowl of a stand mixer fitted with the dough hook, stir together the milk, yeast, and a pinch of the sugar; let sit until
foamy, about 10 minutes. Add the remaining sugar, the melted butter, salt, and egg whites and stir until smooth. Add the flour and mix on medium speed until the dough just comes together. Increase the speed to medium-high and knead until the dough is smooth and pulls away from the side of the bowl, about 8 minutes more. Remove the bowl from the mixer, cover with plastic wrap, and let sit in a warm place until doubled in size, 1 1/2 to 2 hours.
In a large bowl, beat the butter, granulated sugar, and orange zest with a handheld mixer on high speed until smooth. Add the confectioners’ sugar, orange juice, and vanilla and beat until
smooth. Place 1/3 cup in a separate bowl and cover with plastic wrap. Transfer the dough to a work surface and punch it down into a flat circle. Cut the circle into 16 equal pieces, then shape each one into a rough rope and tie into a knot. Place the knots in the larger bowl of orange butter and toss gently with your hands until they’re all coated in orange butter. Transfer them to an 8-inch square glass baking dish, spreading them out evenly, and cover with plastic wrap. Let sit until slightly risen, about 1 hour at room temperature or about 8 hours in the refrigerator (or overnight).
Heat the oven to 350°. Uncover the rolls and, if you refrigerated them, let them sit at room temperature for about 15 minutes to take the chill off, then bake until golden brown and cooked through, 25 to 30 minutes. Remove from the oven and immediately dollop small spoonfuls of the reserved orange butter over the rolls, letting the butter melt on top of and between the rolls. Let cool for at least 15 minutes before serving the