Am not recommending this, or saying it's a good, better or best method, but I saw this done once. You definitely need a fire extinguisher nearby and do it outdoors
Guy worked with maple primarily. As best I recall would make a mix of about 2/3s cup paint thinner, 1/3 cup gasoline and about 1 or 2 tablespoons of motor oil (he actually used chainsaw 'bar and chain' oil). Would mix this up and use a rag to apply to entire surface. Would then dampen a different rag in naphtha. Would use naphtha rag to randomly wipe certain surface areas. He would then use a propane torch to make a somewhat slow pass over entire surface. The areas with the gas/oil mix would get a small flame and then would burn out. The edges darker than the center area. The areas wiped with naphtha rag wouldn't really ignite/burn, but would end up a slightly darker color than the bare wood had been.
His strategy was that the gas would ignite, but the paint thinner and oil would lessen/dampen the flame. Naphtha wiped areas would have much of the oil and flammable stuff wiped away. The finished look showed much of the wood that looked burnished and had a slight amber tone. The edges of each "puddle" were a bit darker, but showed up randomly and added a bit of "character". Interesting look, but not one that I would ever try
Bob "Boardman" Borders