Combine sugar and 2/3 cup of the milk. Give it a quick whisk. Sprinkle yeast on top. Leave for 5-10 minutes until yeast is foamy.
In the bowl of a en electric mixer, combine flour, salt, eggs and rest of the milk. Using a dough hook, add the proofed yeast and knead until the dough is soft and elastic, about 5 minutes.
Add filling and mix until thoroughly combined. Cover with plastic wrap and a kitchen towel. Leave until doubled in size, about 1 hour.
In a small bowl, mix the topping ingredients until thoroughly combined.
Heat a large pot with enough oil for deep frying.
Pinch off some dough and roll into balls. Place in the hot oil and fry until golden brown on all sides. Remove to paper towels to absorb any excess oil.
Immediately roll in cinnamon sugar.