Preheat the oven to 400°F. Line a baking sheet with aluminum foil and spray the foil with non-stick cooking spray.

In a medium saucepan over medium heat, add 1 teaspoon olive oil and 2 cloves minced garlic. Cook, stirring occasionally, until the garlic is fragrant and softened, about 2–3 minutes.

Add 1 tablespoon honey, 1/3 cup balsamic vinegar, 4 teaspoons Dijon mustard, and salt and pepper to taste to the saucepan. Stir to combine.

Bring the mixture to a gentle simmer and cook until the glaze begins to thicken, about 3 minutes. Remove the saucepan from the heat.

Pour the glaze into a heatproof bowl and set aside half of it for finishing the salmon after baking (reserve approximately 50% of the total glaze).

Place the 4 (5-ounce) salmon fillets on the prepared baking sheet. Brush the tops of the fillets with the remaining half of the warm glaze.

Bake the salmon in the preheated oven for 6–10 minutes, until the flesh is opaque and flakes easily with a fork.

Remove the salmon from the oven, brush each fillet with the reserved glaze, garnish with 1 tablespoon chopped fresh oregano, and serve.