Activate the yeast: In a large bowl, combine warm water and yeast. Let stand for 5 minutes, or until foamy.

Prepare the dough: Add flour and salt to the yeast mixture. Knead on a lightly floured surface for 10 minutes, or until dough is smooth and elastic.

First rise: Place dough in a greased bowl, cover, and let rise in a warm place until doubled in size, about 1 hour.

Laminate the dough: Punch down the dough and divide it into 4 equal parts. Rest for 15 minutes.

Create layers: Roll out each dough piece into a thin rectangle. Spread softened butter over the dough. Fold the dough into thirds, like a letter. Rotate the dough 90 degrees and repeat the folding process.

Combine layers: Place one folded dough layer on a lightly floured surface. Add another buttered and folded dough layer on top. Repeat with the remaining dough, creating a stack of four layered dough pieces.

Chill the dough: Wrap the dough in plastic wrap and refrigerate for at least 25 minutes.

Shape and fill: Roll out the chilled dough to about 1/2 inch thickness. Cut into 3-inch squares.

Assemble the rolls: Place a spoonful of grated cheddar cheese and chopped sausage on each square. Bring the corners of the dough together to form a triangle, sealing the edges tightly.

Brush and bake: Brush the tops of the rolls with egg yolk. Bake in a preheated oven at 375°F (190°C) for 30-35 minutes, or until golden brown and crispy.