This is a comment I made back in 2006, which is interesting in its own right.
Vegetarian haggis has been around for at least 100 years, and there is evidence to suggest that the original was veggie – it really is just leftovers plus oatmeal and spices. The oldest example I know of comes from Reform Cookery Book: Up-To-Date Health Cookery for the Twentieth Century by Mrs. Mill, published in 1904. Apart from the butter, which is easily substituted with another fat, the recipe is vegan.
“Fair fa’ yer honest, sonsy face,
Great chieftain o’ the puddin’ race.”
It is to be hoped the shade of Burns will forbear to haunt those who have the temerity to appropriate the sacred name of Haggis for anything innocent of the time-honoured liver and lights which were the sine qua non of the great chieftain. But in Burns’ time people were not haunted by the horrors of trichinae, measly affections, &c., &c. (one must not be too brutally plain spoken, even in what they are avoiding), as we are now, so perhaps this practical age may risk the shade rather than the substance.
For a medium-sized haggis, then, toast a breakfastcupful oatmeal in front of the fire, or in the oven till brown and crisp, but not burnt. Have the same quantity of cooked brown or German lentils, and a half-teacupful onions, chopped up and browned in a little butter. Mix all together and add 4 ozs. chopped vegetable suet, and seasoning necessary of ketchup, black and Jamaica pepper.
It should be fairly moist; if too dry add a little stock, gravy, or extract.
Turn into greased basin and steam at least 3 hours. An almost too realistic
imitation of “liver” is contrived by substituting chopped mushrooms for the lentils. It may also be varied by using crushed shredded wheat biscuit crumbs in place of the oatmeal. Any “remains” will be found very toothsome, if sliced when cold, and toasted or fried.
Interestingly, this recipe is almost identical to modern vegan haggises, which usually involve lentils and kidney beans, plus mushrooms.