In a mixing bowl, combine warm milk, yeast, and a teaspoon of sugar. Let it sit for 5-10 minutes until frothy.
Add flour, sugar, salt, eggs, and butter to the yeast mixture. Knead until smooth and elastic.
Place dough in a greased bowl, cover, and let rise for 1-2 hours until doubled in size.
For the topping, mix butter, sugar, flour, and vanilla extract until smooth.
Divide dough into 12 pieces, shape into balls, and place on a baking sheet. Flatten slightly.
Top each dough ball with a piece of the topping, pressing gently. Score the topping with a knife to create a shell pattern.
Preheat oven to 350°F (175°C). Bake for 15-20 minutes until golden brown.