Once water is boiling, remove from burner and stir in dried porcini mushrooms. Set aside at least 5 minutes. Strain through a wire-mesh strainer into a heat-proof medium mixing bowl. Discard porcinis. Reserve pot. Stem shiitake mushrooms and cut caps into ¼” strips. Cut cremini mushrooms into ¼" slices. Peel and mince shallot. Mince parsley, both stems and leaves. Halve baguette lengthwise and slice each half on an angle, creating four wedges.
Roast the Mushrooms
Place shiitakes and creminis on prepared baking sheet. Toss with 2 tsp. olive oil, ¼ tsp. salt, and a pinch of pepper. Spread into a single layer. Bake until mushrooms are tender, 10-12 minutes. Remove from oven and set aside. While mushrooms roast, begin risotto.
Start the Risotto
Return pot used to make broth to medium-high heat and add 2 tsp. olive oil. Add shallot and parsley (reserving a bit for garnish) to hot pot. Cook, stirring constantly, until fragrant, 1-2 minutes. Add Arborio rice and cook, stirring constantly, until rice is lightly browned, 2-3 minutes. Add 1 cup hot broth to pot with rice. Rice should just be covered by broth. Stir constantly, until nearly all broth is absorbed.
Finish the Risotto
Add another ½ cup broth and stir constantly until broth is nearly all absorbed. Repeat this process, stirring regularly, 18-20 minutes. Taste risotto as you cook, checking for tenderness. When rice has no more "bite" or crunch, it's done. There may be broth left. Remove pot from burner and stir in butter, cooked mushrooms, and Parmesan cheese. Season to taste with salt and pepper. Cover and set aside. While risotto cooks, toast baguette.
Bake the Baguette
Drizzle baguette slices with ½ tsp. olive oil and season with a pinch of salt and pepper. Place directly on oven rack and bake until lightly browned and toasted, 5-7 minutes.
Plate the Dish
Place a serving of risotto on a plate or in a bowl. Garnish with parsley. Serve with toasted baguette.