Heat the milk and butter together in a microwave-safe bowl until the butter is melted and the mixture is warm, about 60–90 seconds.
1 cup milk, ¼ cup salted butter
Stir in the salt and set aside to cool until just warm to the touch (about 120°F–130°F).
1¼ teaspoons kosher salt
In a separate bowl, combine the warm water, about 1 tablespoon of the sugar, and the yeast. Stir and let stand 5–10 minutes, until foamy.
⅔ cup warm water, ½ cup granulated sugar, 1 tablespoon active dry yeast
Add the milk mixture, remaining sugar, eggs, and vanilla to the yeast mixture.
2 large eggs, 2 teaspoons vanilla bean paste
Mix in 1 cup of the flour until combined.
Continue adding flour, about 1 cup at a time, mixing and kneading until a very soft dough forms and begins pulling away from the sides of the bowl. Add the remaining ½ cup flour only if the dough is excessively sticky.
5 to 5½ cups all-purpose flour
Knead with a dough hook on medium speed for about 5 minutes, or knead by hand for 8–10 minutes, until smooth and elastic.
Shape the dough into a ball, place in a lightly oiled bowl, turn to coat, and cover.
Let rise in a warm place until doubled in size, 1–2 hours.