In a larger mixing bowl, add yeast and 1/4 cup sugar to warm water. Stir to dissolve. Add the vanilla and stir to combine. Let the yeast bloom for about five minutes.

Pour the yeast mixture into the mixture bowl of a stand mixer. Use the whisk attachment and gradually add the flour mixture, whisking after each addition. Switch to the dough hook and knead the dough for about five to seven minutes until it forms a smooth ball.

Put the dough into an oiled bowl, cover, and set aside to rise for about 90 minutes or until it has doubled in size. Punch down, cover again, and let it rise for an additional 30 minutes.

Transfer the dough to a well-floured surface. Divide into four large pieces. Pinch into smaller pieces and roll into balls, then place the balls on parchment paper dusted with flour. Repeat with the rest of the dough. This should yield about 24 balls.

Combine the 1 cup sugar and 1 teaspoon cinnamon in a shallow bowl and set aside. This will be the dusting on top of the sfinci.

Heat oil to about 350 degrees in a skillet on the stovetop. Carefully place about six sfinci in the skillet at a time.

Fry about three minutes on each side, flipping once, until the sfinci balls turn golden brown.

Drain on paper towels.

Roll the sfinci in cinnamon sugar.

Serve warm.