Melt the butter or margarine in a pan over medium heat. Stir in the flour and cook for one to two minutes, stirring constantly, until the mixture turns lightly golden.

Add onions or shallot and sauté for 2–3 minutes, until softened. Then stir in

the garlic and cook for 30 seconds until fragrant. Gradually whisk in the milk,

creating a smooth sauce, then add the peas, if using, and let them cook for

three to four minutes, until tender.

Stir in Dijon mustard, tarragon, lemon juice, lemon zest, salt, and pepper,

allowing the sauce to simmer for two to three minutes, until it thickens to your

desired consistency. Set aside and keep warm.

Pat fish dry with a paper towel, as dry skin is key to crispiness. Season all sides with salt, pepper, and garlic powder.

Heat olive oil in a nonstick pan over medium-high heat. Place sea bass skin-side down and press lightly with a spatula for 30 seconds to ensure full contact with the pan. Cook for five to six minutes without moving the fish, until skin is crisp and golden, then flip and continue cooking for three to four minutes, until fish is opaque and cooked through.

To serve, spoon a ladleful of warm tarragon sauce into a shallow bowl and place the crispy sea bass on top. Finish with a sprinkle of lemon zest and a drizzle of lemon juice.