Pour the bread flour into a bowl and add the salt and yeast on opposite sides of the bowl. Stir each in, making sure to keep them separate.

Add the vanilla extract and warm water; begin mixing to form a dough. Adjust with more water or flour as needed to achieve a dry dough.

Turn the dough onto an unfloured surface and knead for 5-10 minutes until very smooth and elastic.

Cube the butter and divide it into three equal parts. Scatter ? of the butter over the dough and knead until fully incorporated. Repeat with the remaining butter.

Gradually knead in some of the extra 3 cups of flour to achieve a non-sticky but soft dough. Transfer to a floured bowl, cover, and let it prove in a warm place for about 45 minutes, or until doubled in size.

Turn the dough onto a floured surface and knead gently. Divide into 10 equal pieces.

Roll out one piece into a skinny rectangle (10-11 inches long). Fold into thirds, turn 90 degrees, and roll out into a rectangle again. Trim ends and cut in half lengthwise to form two strips.

Coat both sides of the strips with granulated sugar and pinch ends together to form two rings. Place on a parchment-lined cookie sheet, spaced 3 inches apart, and chill until ready to bake. Repeat with remaining pieces.

Mix all cake filling ingredients (except melted butter and oil) in a medium bowl to form a dry paste. Add melted butter and oil; mix until smooth. Adjust consistency with milk if too thick.

Fill the chilled rings halfway with the batter.

Bake at 400?F for 20-25 minutes, or until a toothpick inserted into the center comes out clean.

Let cool on a wire rack for at least 20 minutes before serving.