In a pot of salted water, cook the turnips and potatoes until soft. Reserve ½ cup of the cooking water and strain the rest. Add black pepper, reserved water and margarine to pot. Puree with potato masher or immersion blender.

Serve warm or at room temperature with crispy shallots.

Pour oil into a deep saucepan and turn heat to medium. Test heat of oil by placing one shallot inside.  If it browns deeply within first minute, oil is too hot.  Bubbles should form around the shallots, but they should cook and darken slowly for about 20-30 seconds.  If they are browning too quickly, lower flame. 

Once brown, remove with slotted spoon and let dry on paper towel for a few hours. Store in a dark dry area for up to 2 days.