Beurre Blanc and Beurre Monte difference I know that beurre blanc is made with shallots, an acid and butter, while beurre monte is made by just whisking butter in a bit if boiling water.

However, I cannot find a source explaining the difference of where you would use the one but not the other. Is one more a finished sauce, while the other an intermediate step for for other dishes?
The beurre blanc is a final sauce whereas the beurre monte is more of an intermediate sauce for poaching, basting and on occasion, finishing. 

Beurre monte is basically just melted butter with a more homogeneous composition that makes it more suitable for poaching or basting than melted butter (that separates).