Obtaining National and Secure Homeland Operations for Rare Earth Manufacturing Act of 2023 or the ONSHORE Manufacturing Act of 2023 This bill sets forth provisions to support secure supply chains of rare earth elements. A rare earth element means a natural element associated with (1) the metallic element scandium, with atomic number 21; (2) the metallic element yttrium, with atomic number 39; or (3) any of the series of 15 metallic elements between lanthanum, with atomic number 57, and lutetium, with atomic number 71, on the periodic table. The Department of Energy (DOE) must establish a program that provides financial assistance for facilities located in the United States that produce finished rare earth products from purified rare earth elements. Financial assistance may be provided to (1) construct such facilities, (2) support workforce development for the facilities, or (3) support site development and technological upgrade for facilities. The Department of the Treasury may establish the Minerals Security Partnership Fund to support the development and adoption of a secure supply chain for rare earth elements. DOE must also establish an initiative with educational, workforce training, and apprenticeship programs relating to advanced rare earth element mining, separation, processing, metallurgy, and advanced equipment maintenance capabilities. In addition, the President must develop a plan of action for using the authorities available under the Defense Production Act of 1950 to establish or enhance a domestic production capability for finished rare earth products and related technologies.