Not sure I would call it a must do but there there is a local chain called Liguria, 4 spots I think, that is a good place to eat and drink. If you ski you are going to be there at the right time and several resorts are a day trip from the City. 20driver
If you like the coast, Vinya del Mar and Renyaca are worth a visit, and for wines, the area of the Maipo Valley where there are some superb spots. All within easy reach of Santiago.