Warm milk and oil in a large saucepan over medium-low heat. Whisk in brown sugar and vanilla until sugar melts, then remove from heat.
Sprinkle yeast over the warm mixture and let sit for about a minute, until many bubbles form.
Pour mixture into a mixing bowl and fold in 4 cups flour just until combined. Cover with a damp cloth and set in a warm place for an hour to rise.
After dough has risen, fold in remaining flour, baking powder, baking soda, and salt.
Preheat oven to 375°.
Set half the dough on a lightly floured rolling surface. Roll into a rectangle about 1/4-inch thick.
Brush dough with 1/4 cup melted butter. Sprinkle with 1/4 cup brown sugar, 1/2 t. cardamom, and 1/2 orange zest. Spread half the chopped chocolate evenly over the dough.
Roll the dough tightly toward you, starting on a long edge. Place the roll seam-down and slice into 8 even pieces.
Place rolls into a greased pie plate or 8x8 baking dish. Repeat with remaining dough and filling.
Let rolls rest for 15 minutes.
Bake at 375° for 18-22 minutes, until tops are golden brown.
While rolls bake, whisk together all glaze ingredients.
Let rolls cool for 10 minutes, then drizzle with glaze. Serve warm.