In a small bowl, whisk together your ¼ cup low sodium soy sauce, 2 tablespoons light brown sugar, 2 tablespoons olive oil, 1 tablespoon whole grain mustard, 1 teaspoon cajun seasoning, and 2 minced garlic cloves.
In a medium-sized skillet over medium high heat, add 2 tablespoons unsalted butter. Add the sauce and whisk and let reduce until the butter is melted about 2 minutes.
Prepare 1 pound large peeled and deveined shrimp by seasoning with salt and pepper. Add the shrimp to the sauce. Toss and cook in the sauce 4-5 minutes until the shrimp is opaque.