1. In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add halved baby potatoes cut side down and cook for 6-8 minutes until golden. Flip and cook another 4-5 minutes until tender. Season with salt and pepper. Remove and set aside.

2. Pat cod fillets dry with paper towels. Season both sides with salt and pepper. In the same skillet, add another tablespoon of olive oil over medium-high heat. Sear cod for 3-4 minutes per side, until golden and just cooked through. Remove cod and keep warm.

3. Lower heat to medium. Add butter to the skillet and stir in minced garlic. Cook until fragrant, about 30 seconds. Pour in heavy cream and stir in Dijon mustard, chopped rosemary, and red pepper flakes if using. Let simmer for 3-5 minutes until the sauce thickens slightly.

4. Return the potatoes to the skillet and gently toss to coat in the sauce. Nestle the cod fillets on top. Spoon sauce over the fish and finish with a squeeze of lemon juice. Serve immediately with extra rosemary or lemon wedges on the side.