Pot Roast with Porcini and Mashed Potatoes

I make pot roasts flavored with dried porcini all winter long. This is my basic recipe. Sometimes I add carrots, cut about 2 inches long and added in the last half hour of cooking; sometimes I add a cup of dried white beans once the pot is set for the long boil; sometimes I throw in a handful of frozen peas during the last 15 minutes of cooking. Other times, I add warm spices, like nutmeg and cinnamon, or hot peppers. The recipe varies all the time, but I always like to include a mash.