Drop a blaze rod and an iron/diamond pick/axe/shovel on top of an enchantment table while you have 10 xp levels to enchant it with the ability to smelt blocks just by mining them.

Smelt-able blocks include:
potato crops -> baked potatoes
kelp -> dried kelp
iron and gold ore -> ingots
sand -> glass
cobblestone -> stone
clay -> bricks
netherrack -> nether brick item
stone bricks -> cracked stone bricks
dyed terracotta -> glazed terracotta
cactus -> cactus green dye
logs and all permutations -> charcoal
chorus flower -> popped chorus fruit
wet sponge -> dry sponge
sea pickle -> lime green dye

Instruction file included. Should be multiplayer compatible but needs testing. I'm open to suggestions for improvements.