Preheat oven to 350 degrees.
Roll out dough and place in a tart pan.
In a medium saute pan, place onions and cook until translucent. Add shredded carrot and mushrooms. Turn heat down and add lentils. Heat to warm and add the horseradish, tamari and cumin. Adjust seasoning. In a separate bowl, combine eggs and cream. Pour over Lentil mixture.
Pour into tart pan and bake at 350 for about 20 minutes, or until done.