Hello, yes it's possible. But until now i've seen grow with this way just oysters (P.ostreatus and P.citrinopileatus).
You have to keep overnight the chopped straw(never seen with sawdust) in a mixture of water and hydrated lime..this will increase a lot the pH of the substrate so molds will not attach it. Stamets suggest to add 2-4 pounds of lime every 50 gallons of water(about 0.5-1.0% in weight of lime to the weight of the water). So you drain well an inocule.After 3-4 days the colonization is visible and after 7-10 days the straw is fully colonized.