Classic shrimp scampi is garlic, butter, white wine, and lemon. I add white miso to the sauce here. It dissolves into the wine and you cannot see or taste it as miso. What it does do is make the sauce taste richer and more complete than the original.
Cook pasta in well-salted water until just under al dente. Reserve ½ cup pasta water before draining.
Pat shrimp dry. Season lightly with salt and pepper. Heat 1 tablespoon butter and the olive oil in a large skillet over medium-high. Sear shrimp about 2 minutes or until they are just beginning to turn from translucent to pink. Transfer the shrimp to a plate and set aside.
Reduce heat to medium. Add remaining butter and garlic to the same pan. Cook 2 minutes until garlic is soft and fragrant but not browned.
Whisk miso into white wine until dissolved. Pour into the pan. Scrape up any browned bits. Simmer 2 minutes until reduced by half.
Add lemon juice, red pepper flakes, and pasta water. Add drained pasta and toss to coat. Return shrimp to the pan. Toss everything together over low heat for 1 minute until the sauce clings to the pasta and the shrimp are pink and heated through.