1. Peel shrimp; devein, if desired.
2. Pierce potatoes several times with tines of a fork. Place on a microwave-safe plate; cover with damp paper towels.
3. Microwave potatoes at HIGH 10 to 12 minutes or until tender. Let stand 5 minutes. Cut into 1-inch cubes.
4. Attach fruit and vegetable strainer attachment to electric stand mixer according to manufacturer's instructions. Strain potatoes into a bowl according to manufacturer's instructions. Scrape any remaining potato puree from strainer tray into bowl. Stir together potato puree, milk, and next 3 ingredients. Cover and keep warm.
5. Cook bacon in a large skillet over medium heat 8 to 10 minutes or until crisp. Remove bacon, and drain on paper towels, reserving 2 tablespoons drippings in skillet. Crumble bacon.
6. Sauté mushrooms in hot drippings 8 minutes or until tender. Remove from skillet.
7. Toss shrimp in cornstarch. Add shrimp to skillet, and sauté over medium heat 3 to 5 minutes. Add garlic and next 3 ingredients. Increase heat to medium-high, and cook 1 minute or just until shrimp turn pink.
8. Spoon sweet potato mixture onto a serving platter. Top with shrimp mixture and mushrooms. Sprinkle with bacon. Garnish, if desired.