In a heavy-bottomed pot or Dutch oven, melt the butter and saute the bacon and shallots over medium-low heat for 5 minutes. Add the mushrooms and saute for another 5 minutes. Add the rice and stir to coat the grains with butter. Add the wine and cook for 2 minutes. Add 2 full ladles of the warm chicken stock to the rice plus the saffron, salt and pepper. Stir and simmer over low heat until the stock is absorbed, 5 to 10 minutes. Continue to add the stock mixture, 2 ladles at a time, stirring every few minutes. Each time, cook until the mixture seems a little dry before adding more of the stock mixture. Continue until the rice is cooked through, about 25 to 30 minutes.