In a large bowl, combine Bisquick, buttermilk, and sugar in a bowl using a fork. Mix just until all combined to create a dough.
In a medium bowl, combine brown sugar, granulated sugar, cinnamon, and nuts in a separate bowl. Add 2 tablespoons melted butter and stir to moisten. Set aside.
Generously flour rolling surface.I know it seems like a lot but trust me, this is a sticky dough. Turn the dough out onto the surface and start patting into a rectangular shape with your hand. Flour your hand well also.
Use a rolling pin to the thin dough to about 1/2 inch thickness. Do not over-roll, the dough will stick.
Once rolled out, pour 3/4 cup melted butter over the entire surface then spread with a pastry brush to even out and get to the edges.
Sprinkle sugar/nut mixture over butter.
Start rolling dough from the long end.
Slice into 1 inch to 1/2 inch slices. I used dental floss to slice mine. It really does work, without mushing the pastry.
Transfer slices to a well-greased (sprayed) 9 x 13 pan. I used a spatula to make it easier.
Bake in a preheated 375-degree oven for 25-30 minutes, until just golden brown on tops.
Let sit for 5 minutes before serving.
Combine powdered sugar, milk, and vanilla until desired consistency and drizzle over top of rolls.