Directions

1. Make the dough: Sprinkle yeast over warm water in a small bowl. Let stand until foamy, about 5 minutes.
2. Whisk milk, butter, eggs, honey, salt, and vanilla with a mixer on medium speed. Add yeast mixture, and whisk for 1 minute. Switch to dough hook, reduce speed to low, and add 4 cups flour. After flour is incorporated, raise speed to medium, and continue kneading.
3. Add remaining flour, 1/2 cup at a time, mixing until dough no longer sticks to the bowl. Raise speed to medium-high, and knead for 10 minutes. (Alternatively, knead by hand until smooth, 15 to 20 minutes.)
4. Turn dough out onto a lightly floured surface, and knead until dough is very smooth, about 5 minutes. Transfer to a lightly oiled bowl, cover with plastic, and set aside in a warm, draft-free spot until doubled in size, about 1 hour.
5. Make the filling and topping: Melt butter in a saucepan over medium heat. Stir in honey, corn syrup, and sugar, bring to a gentle simmer, then remove from heat. Let cool. Combine mascarpone and creme fraiche in a bowl.
6. Punch down dough. Turn out onto a lightly floured surface, and divide into 3 portions. Roll each into a ball. Freeze 2 for up to 3 months (thaw in the refrigerator before using). Roll remaining dough into a 10-by-13 1/2-inch rectangle. Brush lightly with honey, spread mascarpone mixture evenly on top, leaving a 1-inch border, and sprinkle with pecans. Starting on 1 long side, roll dough into a log. Pinch along seam to seal. Cut into nine 1 1/2-inch-thick slices.
7. Pour honey mixture into an 8-inch square baking pan. Place buns, cut sides down, in pan, 3 to a row. Let buns rise in a warm, draft-free spot until doubled in size, 30 to 40 minutes.
   
8. Preheat oven to 375 degrees. Place oven rack in lower third. Bake buns, rotating halfway through, until brown and bubbling, about 1 hour. (If buns darken too quickly, cover with foil.) Set a wire rack on a baking sheet. Immediately invert buns onto rack. Drizzle with honey, and serve warm.