Which sculpture technique lets a hollow bronze be cast from a model that is destroyed in the process?

Lost-wax casting. A wax model is built over a core, invested in clay, and heated until the wax runs out; molten bronze fills the space the wax occupied. The model is consumed, which is why every direct lost-wax casting is unique, and why the technique demands getting it right in wax.

It has been in use for six thousand years and has been invented independently more than once - in the Indus valley, in West Africa, in China, in the Andes. The Benin brasses, the Riace bronzes and the Chola bronzes of south India are all this process. An indirect version, taking a mould from the original model first, allows editions and is what modern foundries use.

It is also why so little classical bronze survives. Bronze is worth melting down, so almost every Greek bronze known was recovered from a shipwreck rather than from land, and most of what is in museums is Roman marble copies of lost bronze originals - which is why classical sculpture is popularly imagined as white stone, when a great deal of it was metal, and the marble was painted.