In a small bowl, combine warm milk, sugar, and active dry yeast. Stir gently and let it sit for 5-10 minutes until frothy.

In a large mixing bowl, whisk together all-purpose flour and salt. Create a well in the center and pour in the frothy yeast mixture and melted unsalted butter.

Gradually mix in the flour with the yeast mixture using a wooden spoon until a rough dough begins to form. Knead the dough until smooth.

Transfer the dough onto a floured surface and knead for an additional 5-10 minutes until elastic and smooth. Place in a greased bowl, cover, and let rise until doubled in size.

Sauté spinach over medium heat until wilted. In a bowl, scramble eggs, add to spinach along with diced ham, and cook until eggs are set. Mix in cheddar cheese until melted.

Punch down the risen dough and divide it into 12 equal pieces. Roll each piece into a rectangle, spoon the filling in, seal, and shape into balls.

Place rolls on a greased baking sheet, cover, and let them rest for 30-45 minutes until puffed.

Preheat oven to 350°F. Brush rolls with egg wash if desired. Bake for 20-25 minutes until golden brown.

Let rolls cool on a wire rack for about 10 minutes before serving.