Step 1Heat the oven to 375 degrees. Toss the breadcrumbs with 1 tablespoon olive oil. Spread them on a baking sheet, and toast for 8 to 10 minutes, stirring once or twice, until golden brown and crispy. Set aside.
Step 2If the mushrooms are large, tear them into smaller pieces. Heat two large saute pans over high heat for 2 minutes. Swirl in 2 tablespoons olive oil to each pan and wait 1 minute. Add 1 tablespoon butter to each pan; when it foams, scatter the mushrooms into the pans. (Be careful not to crowd the pans. There should be a single layer of mushrooms. It's better to do more batches than to crowd the mushrooms.)
Step 3Season with salt, pepper and thyme leaves. Add the shallots and saute together with the mushrooms about 5 minutes, stirring occasionally, until the mushrooms are tender and a little crispy. (The cooking time will depend on the particular mushrooms you are using.)
Step 4Reduce the heat to medium-high and use a wooden spoon to push the mushrooms to one side of the pan. Add half the remaining tablespoon of butter to each pan. When it foams, add half the garlic to each pan. Let it sizzle and then stir to incorporate it with the mushrooms. Add parsley and toss to coat well. Taste for seasoning and arrange on plates. Sprinkle breadcrumbs over the mushrooms and serve.