In the bowl of a stand mixer fitted with a dough hook, combine the yeast, 1 tablespoon sugar, and 1 cup of warm water. Let stand for 5 minutes until it becomes foamy. Add the remaining ¾ cup sugar, 3 eggs, salt, and vanilla, and mix well. Add the remaining 1 cup of warm water. 

With the mixer on low, add half of the flour, mixing until just combined. Add half of the oil, then mix to combine. Repeat with the remaining flour and oil. Turn the mixer to medium, and mix until the dough becomes smooth and pulls away from the sides, about 8 minutes.

Transfer the dough to a large oiled bowl, and cover with a damp towel or plastic wrap. Let rise in a warm place for 1 hour. After it’s risen, knead down the dough in the bowl for a few turns, and re-cover for 1 hour. Repeat once more, for a total rise time of 3 hours.

Line 2 baking sheets with parchment paper. Mix 2 eggs with 1 tablespoon of water to make an egg wash.

Once the dough has risen, transfer to a lightly oiled surface. 

Roll the dough out to a large rectangle, about 10 inches wide and 18 inches long. Cut evenly into 6 strips. Roll each strip to be 3 inches wide. Working one strip at a time, spread 1 tablespoon of guava jelly in a line along the side of one length, and lightly brush the other side of the length with the egg wash. Roll the strip so that it seals in the jelly, then pinch closed along the egg wash edge to seal completely. Using your hands, roll into longer strips, about 18-20 inches long. Lightly dust the strips with flour to avoid sticking.

Once you have filled and sealed all 6 strips, form into two braided loaves, making sure to keep the seam sides of each strip towards the inside of the braid to prevent leaking. Place each loaf on a parchment-lined baking sheet, loosely cover with plastic or a towel and let rise for 40-45 minutes more, until the dough springs back when lightly poked.

Preheat the oven to 350 degrees. Lightly brush the loaves with egg wash, and bake for 40 minutes. Halfway through baking, switch the loaves’ position in the oven: the lower loaf moves to the upper rack, and vice versa. This will help them bake evenly and not burn. Bake until golden. Let cool and serve.