Behold! My single chunk branch mining base. The staircase has 4 stairs per turn, which fits well into my standard spacing when mining. It fits snugly into a single chunk, which helps when using mods with complex machines -- since those really shouldn't cross borders, if it can be helped.
Here we go, to the East we have the wall of the base and the beginnings of the branch mining operation. This is the same on the other walls, of course, simply rotated.
So at the end of each of the branches, we make a corner -- the branches become concentric squares.
Finally, we stack the branches, so as to complete the pattern. Here's a cross-section view. White wool are the tunnels, gray wool are where we cut rough stairs into the wall, so as to access the next level up. My mnemonic when facing the wall is "upright". I do this on both sides of the tunnel, so there's a reversed set of stairs going up the other side.