Step 1In the bowl of a stand mixer, or in a large bowl, combine the yeast and one-half cup water with 2 tablespoons flour. Set aside until the yeast begins to bubble, 5 to 10 minutes.
Step 2Using the paddle attachment, or with a hand mixer, blend in the remaining water and egg until combined. With the mixer running, add the margarine and sugar.
Step 3Stir in the flour, a spoonful at a time, until incorporated. Remove the dough to a lightly floured board and knead until soft and elastic, 8 to 10 minutes.
Step 4Place the dough in a large, oiled bowl and loosely cover. Set aside until doubled in size, about an hour.
Step 1While the dough is rising, in another mixing bowl, beat the sugar and margarine together until fully combined. This makes about 1 3/4 cups remonce.
Step 1In the bowl of a stand mixer, or in a large bowl, whisk the powdered sugar together with 1 tablespoon water. Continue to add water until a thick glaze forms. Cover the surface of the frosting with plastic wrap (this will keep the frosting from drying out) and set aside.
Step 1Heat the oven to 425 degrees.
Step 2Divide the dough into 4 pieces. Place 1 piece of dough on a lightly floured work surface (keep the remaining 3 loosely covered with plastic wrap so they do not dry out). Roll the dough into a rectangle about 12 inches long and 10 inches wide. Spread one-third cup plus 2 tablespoons filling (the remonce) over the rectangle, then spread a scant one-fourth cup custard over the rectangle. Sprinkle one-half teaspoon cinnamon over the custard, then use a spatula or the back of a spoon to gently combine all the fillings, spreading them evenly over the rectangle.
Step 3Carefully roll the dough into a tube. Place the tube onto a parchment-lined baking sheet and slice most of the way through the tube crosswise into pieces just over three-fourths-inch thick, being careful not to slice all the way through. Flatten each slice to one or the other side, alternating between each to form a Christmas tree pattern.
Step 4In a small bowl, whisk together the egg and salt. Brush the egg over the formed kringle and lightly cover it with plastic wrap. Repeat with the remaining pieces of dough to form a total of 4 kringle. Set the kringle aside in a warm place until they puff and almost double in volume, about 1 hour.
Step 5Bake the pieces until golden-brown and baked through, 8 to 10 minutes. Cool slightly, then frost with the glaze.