Wash the beets as well as the greens very well. 

Boil the beets (only the deep purple roots) in a pressure cooker for thirty minutes. 

Boil the greens separately. 

When the beets are tender, remove them from the pressure cooker. Peel the skin and cut into slices.

When the greens are done, cut them in half. 

Place all in airtight tupperware together with oil, garlic, vinegar and salt. It's best if you set it aside overnight so that the ingredients combine. 

Serve on the side, with fish, potatoes or whatever else you might like.