A full Gaufre de Liège recipe did not appear until 1921. Earlier recipes contained pieces of the tradition’s ingredients, but the complete named preparation was documented only in the early 20th century.
The Liège waffle is a dense, sweet Belgian waffle made from a brioche-like raised dough. Pearl sugar is mixed through the dough, then caramelizes in the waffle iron, producing its characteristic crunch, chew, and irregular caramelized crust. The modern style is therefore more than simply an old waffle recipe with sugar sprinkled on top.
The historical trail is gradual. Antoine Beauvilliers introduced brioche dough as a waffle base in 1814 and used crushed block sugar as a garnish. Antonin Carême incorporated gros sucre into several waffle variations in 1822. In 1834, Leblanc published a complete recipe for gaufres grêlées, but it was not yet identified as a full Gaufre de Liège recipe.
This is why claims that the Liège waffle was fully recorded in 1740, 1814, or 1834 overstate the evidence. Those dates mark related developments, not the complete recipe.