In a small bowl, combine warm milk, sugar, and yeast. Stir to dissolve and let sit for about 5 minutes, or until frothy.

In a large bowl, mix melted butter, salt, and eggs. Add the yeast mixture and vanilla extract. Gradually add the flour, one cup at a time, until the dough forms a ball.

Knead the dough on a floured surface for about 5-7 minutes until smooth and elastic. Place the dough in a lightly greased bowl, cover, and let it rise for 1-1.5 hours or until doubled in size.

Preheat the oven to 375°F (190°C) and grease a baking dish or line it with parchment paper.

Punch down the dough and roll it out into a large rectangle (about 12×18 inches).

Spread softened butter over the dough, then sprinkle the brown sugar and cinnamon mixture evenly over the top. Add chocolate chips if using.

Roll the dough tightly into a log and cut it into 12 equal pieces.

To shape the bunny buns, take each piece and roll it into a ball. For each ball, cut two small slits at the top to form bunny ears, then pinch the sides together to shape the body and head of the bunny.

Place the shaped buns on the prepared baking dish, leaving space between each bun. Cover with a clean towel and let rise for 30-45 minutes.

Brush the buns with the egg wash (1 beaten egg with a splash of water).

Bake for 15-18 minutes or until golden brown and cooked through.

While the buns are baking, mix powdered sugar and milk together to make an optional glaze for icing.

Let the buns cool slightly, then drizzle with the glaze or enjoy as is.