Add 1 tbsp olive oil to a 12" skillet on medium high heat and once the oil shimmers, add the shrimp shells. Stir occasionally until the shells start to brown, 3 to 4 minutes.
Remove the skillet from the heat and add the white wine and thyme sprigs. Return to the heat and simmer the wine 4 to 5 minutes, stirring occasionally.
Remove from the heat and strain the sauce into a bowl. Use a spoon or spatula to squeeze all the liquid from the shells. Discard shells and thyme.
Wipe the same skillet clean with paper towels, return to the stove on medium heat, add the remaining 1 tbsp of olive oil, pepper flakes, pepper, and slivered garlic. Stir until fragrant, about 1 minute, then add the wine sauce and bring to a simmer.
Add the shrimp to the skillet and cook, turning with tongs, until the shrimp is opaque, 5 to 7 minutes.
Remove the shrimp from the skillet to a dish, then mix the cornstarch with the lemon juice and add to the sauce, stirring until thickened, 1 minute.
Add the pats of butter to the sauce and stir to melt, then stir in the chopped parsley. Add shrimp to the sauce and toss to coat.
Serve alone or over pasta, mashed potatoes, quinoa, or any other grain of choice. Garnish with grated parmesan cheese and lemon wedges.