Heat olive oil in a large pot over medium heat. Sauté onion, carrots, and celery for 5-7 minutes until softened, then stir in minced garlic for another minute until fragrant.

Sprinkle flour over the vegetables, stirring constantly for 1-2 minutes to create a roux.

Gradually whisk in seafood broth, milk, and heavy cream until smooth. Bring to a gentle simmer, stirring occasionally, until the sauce thickens slightly (5-7 minutes).

Reduce heat to low and add shrimp, white fish, peas, parsley, Old Bay seasoning, salt, and pepper. Cook for 3-5 minutes until shrimp are pink and fish is opaque, then remove from heat.

Preheat oven to 400°F (200°C) and pour the seafood filling into a 9x13 inch baking dish.

In a large bowl, whisk together flour, baking powder, salt, garlic powder, and cayenne pepper.

Cut in cold butter until the mixture resembles coarse crumbs, then stir in shredded cheddar cheese.

Pour in cold buttermilk and mix just until a shaggy dough forms, being careful not to overmix.

Drop spoonfuls of biscuit dough evenly over the warm seafood filling (about 8-10 biscuits).

Bake for 20-25 minutes, or until biscuits are golden brown and cooked through, and the filling is bubbly.

While baking, melt 1 tablespoon of butter in a small bowl and stir in minced garlic and chopped parsley for the glaze.

Once out of the oven, brush the warm biscuits generously with the garlic butter glaze. Let rest for a few minutes before serving.