In a small mixing bowl, add yeast, warm water, and sugar. Let it sit until foam forms - about 10 minutes.
In the bowl of a stand mixer, add eggs and mix until fluffy. Add milk, evaporated milk, butter, sugar, and yeast mixture. Mix until combined.
Slowly add flour and salt to the mixture, mixing as you add. Continue to mix until well combined and smooth.
Transfer dough to a lightly greased mixing bowl, cover with a tea towel, and let rise until doubled in size - about 1 hour.
Add dough to a floured surface and roll out to about 1 inch thickness. Use a circle cookie cutter about 3-4 inches wide and cut out dough. Place onto a greased cookie sheet, cover with a tea towel, and let rise until doubled in size (about 1 hour).
Place sugar in a large bowl and set aside.
In a medium saucepan over medium heat, add oil and heat until about 375°F. Add dough rounds to the oil, a few at a time, and fry until golden brown (about 5-7 minutes on each side).
Remove malasadas onto a paper towel-lined plate. Let cool slightly and then toss in the sugar mixture. Add fillings if desired.