Preheat oil to 350°F.
In a mixing bowl combine sugar and cinnamon until completely combined. Set aside.
In a small bowl combine both milks together and stir to create a luke warm milk. (doing this will prevent you from having to wait for your scalded milk to cool)
In a small bowl, combine the yeast and water and allow to sit for 5 minutes. (to activate the yeast).
Place sugar and shortening into a mixing bowl (or in a stand mixer, fitted with a paddle attachment) and cream together. Add sweet potatoes and continue to cream until fully incorporated.
Add eggs, milk, yeast water, and salt and continue to mix until well combined. Gradually add flour, 1 cup at a time and continue to mix until dough forms.
Dump dough into a lightly floured surface and knead until smooth but sticky dough forms, about 5 minutes. Place dough into a lightly greased bowl and cover with a damp towel or plastic wrap and set in a warm area until doubled in size, about 1 hour.
Punch the dough down and dump onto a lightly floured surface once again. Roll dough into a ½ inch thick slab.
Using a 3 inch circle cutter cut spudnuts from the slab and poke a hole in the center of each with your fingers (handle gently to ensure you don’t deform your spudnuts) place onto a baking sheet with lightly greased parchment.
Cover with plastic wrap and place in a warm area until spudnuts double in size.
Carefully remove spudnuts from parchment and slide into the oil, 2 to 3 at a time. Fry each spudnut for about 3 minutes on each side or until a light orange-golden color.
Drain spudnuts onto paper towels and while still warm, lightly brush each with melted butter on both sides, and toss in cinnamon-sugar mixture until fully coated. Serve immediately or store in an airtight container for up to three days.