Make the sponge by mixing ingredients in bowl and letting sit for 1/2 hour.
In a standing mixer
, fitted with a dough hook, add the sponge. Add in the flour, egg, egg yolks, salt, and sugar. Add any additional flour to make smooth dough
. Place in oiled bowl, cover and set aside until doubled in volume. Punch down and let rise (covered) again.
down and roll out into a rough triangular shape that is about 1 1/2 feet and 1/2-inch thick. Paint with melted butter. Mix together sugar, cinnamon and hazelnuts. Sprinkle on. Roll up and press into well-buttered bundt pan
. Let rise until doubled.
Preheat oven to 375 degrees F.
Bake for 40 minutes. Let cool then remove from pan. Cook together butter, sugar
, and liqueur. Paint on top. Sprinkle with nuts.