This paper introduces a conceptual interior design framework - Multi-Touch Mixed Reality (MTMR), which integrates mixed reality with the multi-touch tabletop interface, to provide an intuitive and efficient interface for collaborative design and an augmented 3D view to users at the same time. Under this framework, multiple designers can carry out design work simultaneously on the top view displayed on the tabletop, while live video of the ongoing design work is captured and augmented by overlaying virtual 3D furniture models to their 2D virtual counterparts, and shown on a vertical screen in front of the tabletop. Meanwhile, the remote client's camera view of the physical room is augmented with the interior design layout in real time, that is, as the designers place, move, and modify the virtual furniture models on the tabletop, the client sees the corresponding life-size 3D virtual furniture models residing, moving, and changing in the physical room through the camera view on his/her screen. By adopting MTMR, which we argue may also apply to other kinds of collaborative work, the designers can expect a good working experience in terms of naturalness and intuitiveness, while the client can be involved in the design process and view the design result without moving around heavy furniture. By presenting MTMR, we hope to provide reliable and precise freehand interactions to mixed reality systems, with multi-touch inputs on tabletop interfaces.