In a large skillet, melt butter over medium heat. Add onion, celery, and carrots; sauté until softened, about 5 minutes.

Stir in flour and cook for 1 minute. Gradually whisk in seafood stock and bring to a simmer.

Add shrimp, scallops, peas, heavy cream, lemon juice, thyme, salt, and pepper. Cook until seafood is cooked through, about 5-7 minutes.

Preheat oven to 425°F (220°C). In a mixing bowl, combine flour, baking powder, garlic powder, and salt.

Cut in cold butter until mixture resembles coarse crumbs. Stir in cheese and milk until just combined.

Drop spoonfuls of biscuit dough over the seafood filling in a baking dish.

Bake in preheated oven for 20-25 minutes or until biscuits are golden brown.

Let cool for 5 minutes before serving.