In a large mixing bowl, combine the flour, salt, sugar, and yeast. Mix well.
In a separate bowl, whisk together the softened butter, warmed milk, egg, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and mix until a dough forms. Knead the dough on a floured surface for about 5 minutes until smooth.
Place the dough in a greased bowl, cover with a kitchen towel, and let it rise in a warm place for about 1 hour or until doubled in size.
While the dough is rising, prepare the filling by mixing the diced apples, brown sugar, cinnamon, lemon juice, and cornstarch in a bowl. Set aside.
Preheat the oven to 375°F.
Once the dough has risen, punch it down and roll it out on a floured surface into a rectangle about 1/4 inch thick.
Spread the apple filling evenly over the dough, leaving a small border around the edges.
Roll the dough tightly from one long side to the other, pinching the edges to seal. Shape the roll into a ring and place it on a greased baking sheet.
Bake in the preheated oven for 25-30 minutes or until golden brown.
While the kringle is baking, prepare the glaze by whisking together the powdered sugar, milk, and vanilla extract until smooth.
Once the kringle is done baking, let it cool for about 10 minutes before drizzling with the glaze. Sprinkle with chopped nuts if desired.