1. In a large skillet, melt 1 tablespoon butter over medium-high. Add shrimp and garlic; cook, tossing, until shrimp starts to turn pink on the outside but is still translucent on the inside, about 2 minutes (shrimp will finish cooking in step 3). Transfer to a plate; set aside.

2. Reduce heat to medium. In same skillet, melt remaining butter. Add shallot; cook until softened, 1 to 2 minutes. Add flour; cook 30 seconds, whisking constantly. Gradually add wine, broth, and mustard, whisking constantly. Simmer until it is as thick as heavy cream, about 5 minutes.

3. Using a fine-mesh sieve, strain sauce; discard solids. Return sauce and shrimp to skillet. Bring to a simmer, and cook until shrimp are opaque throughout, about 2 minutes; season with salt and pepper. If desired, serve over rice and garnish with thyme leaves.