Preheat the oven to 375ºF. Spray 10 regular muffin tins with nonstick cooking spray.

In a large bowl, mix together the buttermilk, 1/2 cup of the brown sugar, the egg, and the vanilla.

Once fully combined, add the 3 cups of flour, baking soda, and salt. Mix until the dough comes together. It will be a stiff dough, and it will still have some shaggy edges. There may be a bit of the flour that is not mixed in yet.

Flour a counter or a work surface. Turn the dough out onto the surface. Knead a few times until the dough is fairly smooth and not sticking to your hands.

Roll the dough out into a 10-inch by 20-inch rectangle. Spread the butter on top of the dough, then sprinkle over the remaining 1/2 cup of brown sugar and the cinnamon.

Roll the dough into a 20-inch log. If needed, cut the edges off (if they are ragged) then pull the log back to 20 inches long. Cut the dough into 10 2-inch slices.

Place each of the rolls in a muffin tin, cut side up.

Bake until the muffins are golden brown, about 20 minutes.

While the muffins are baking, make the glaze by whisking together the powdered sugar and the cream. Start with 3 tablespoons of cream, and add more as needed, until you reach your desired consistency.

Once the muffins are baked, let them sit for 5 minutes, then drizzle the glaze over the top.