You can use a tool to edit your save (you create a game, save and quit) to modify everything, even you actual progress, and select the mission you want.

You can try with **Gibbed Mass Effect 3 Save Editor**, which is the most popular an easy-to-use editor. Here how to use it: http://benchmark3d.com/mass-effect-3-save-game-editor

Here you have the mission code: 
>59915	Priority: Palaven