Preheat your oven to 375 °F (190 °C). Butter an 8-inch square baking dish (or similar) and set aside.

In a large bowl, add the 3 cups self-rising flour. Cut in the ½ cup softened butter using a pastry blender or two knives until the mixture resembles coarse crumbs.

Stir in the 1¼ cups buttermilk until a thick dough forms. Let it rest in the bowl while you prepare the filling and glaze.

In a small bowl, melt the ½ cup butter for the filling. Once melted, whisk in 1 cup dark brown sugar and 2 tbsp cinnamon until smooth and combined. Set aside.

In a medium bowl, whisk together the 3 cups powdered sugar, 2 tsp vanilla, and 1 cup buttermilk to make the glaze. Set aside.

On a lightly floured surface, roll the dough into a rough 16×16-inch square. Cut the dough into 1-inch wide strips, then cut each strip in half.

Spread a few tablespoons of the cinnamon filling over the bottom of the prepared baking dish. Arrange enough dough strips over the filling so that the bottom layer is fully covered and the strips are touching.

Spread about ¼ cup of the filling over the dough layer. Drizzle about ½ cup of the glaze over that layer.

Repeat layering: dough strips → filling → glaze. Continue until you have three layers in total, ending with a top layer of dough covered with filling and glaze. Reserve about ¼ cup of glaze for drizzling after baking.

Bake for 30-35 minutes or until the top begins to crisp and brown.

Allow to set for at least 10 minutes before serving. Just before serving, drizzle the reserved glaze over the top.