Activate the yeast (only if using active dry yeast): In a medium bowl, combine 2 teaspoons active dry yeast, 2 tablespoons sugar, and 1 cup warm water. Stir and let sit for 5-10 minutes until foamy. (Skip if using instant yeast.)
Dry ingredients: In a large bowl or stand mixer, whisk together 3¼ cups bread flour and 1 teaspoon kosher salt (or ½ teaspoon table salt). If using instant yeast, add it now.
Wet ingredients: Add 1 egg, ½ cup condensed milk, and 2 tablespoons neutral oil to the yeast mixture. Mix until smooth. If using instant yeast, add 1 cup warm water and 2 tablespoons sugar here.
Mix dry and wet Ingredients: Pour the wet ingredients into the flour mixture. Stir until a sticky dough forms.
Knead the dough: If using a stand mixer, knead on medium speed for 12-15 minutes. The dough will start sticky but will eventually form a smooth, stretchy ball. When it pulls away from the sides of the bowl, it's ready.If kneading by hand, place the dough on a floured surface and knead for 20-25 minutes until smooth and stretchy. Add a little flour if the dough gets too sticky. The windowpane test: Take a small piece of dough and gently stretch it. If it stretches without tearing and you can see light through it, the dough is ready.If it tears, knead the dough more. If it’s tough and hard to stretch, it’s over-kneaded. Let it rest for 30 minutes to relax and make shaping easier. First rise: Form the dough into a ball and place it in a bowl lightly coated with oil so it doesn't stick. Cover with a towel or plastic wrap and set it in a warm, draft-free spot. Let it rise for 1-2 hours, or until it doubles in size.
Prepare the filling: In a bowl, mix 1 cup breadcrumbs, ½ cup softened butter, ¾ cup brown sugar, 1 teaspoon vanilla extract (optional), and a pinch of salt (if using unsalted butter). Stir until well combined.
Divide the dough and add the filling: Gently press down on the risen dough to release air, then cut it in half and each half into 8 equal parts.Flatten each piece into a 6x3-inch rectangle or oval. Spread 2 tablespoons of the sweet filling evenly, leaving a small border around the edges. Shape the dough: Roll each piece of dough into a log, making sure the filling stays inside. Tuck the edge at the bottom to seal it. Coat the log evenly with breadcrumbs.
Second rise: Place the rolls on a parchment-lined baking sheet, leaving space between each. Cover them and let them rise until they’re puffy, about 30 to 45 minutes.
Bake: Preheat your oven to 400°F (205°C). Once it’s heated, bake the rolls for 5 minutes. Then, lower the temperature to 350°F (175°C) and bake for another 13-15 minutes, or until golden brown.