Start by heating a wide skillet over medium-low heat and add the olive oil. Once the oil shimmers and releases a fragrant aroma, spread the thinly sliced garlic in the pan.
Cook the garlic slowly, stirring often, until it becomes golden around the edges and fragrant—this takes about 2-3 minutes. Be careful not to let it burn, as burnt garlic can turn bitter.
Increase the heat to medium and add the shrimp to the pan. Cook for 2-3 minutes on each side until they turn pink, firm, and slightly curled.
Sprinkle the red chili flakes over the shrimp and stir quickly to coat, releasing a little heat and color into the sauce.
Pour in the fresh lemon juice, deglazing the pan and scraping up any browned bits from the bottom. Let the sauce bubble gently and thicken slightly, about 30 seconds.
Add a small knob of butter if using, stirring until melted into the sauce for extra richness. Taste and adjust with salt or more lemon if needed.
Remove the skillet from heat and sprinkle the freshly chopped parsley over the shrimp and sauce. Toss gently to combine and let sit for a minute to meld the flavors.
Serve immediately while hot, spooning the fragrant garlic sauce over the shrimp. Enjoy the smoky, aromatic flavors that make this dish so satisfying.