Preheat oven to 350°F.

Bring a medium pot of water to a boil. Add diced carrots and cook for 5-7 minutes until fork-tender but still slightly firm. Drain and set aside.

Heat 1 tablespoon olive oil in a large skillet over medium heat until shimmering. Add garlic and cook for 30 seconds until fragrant (reduce heat if it starts to brown).

Add cooked carrots and frozen peas to the skillet. Stir to combine, then transfer to a 6x8-inch baking dish.

In the same skillet, heat 1 tablespoon olive oil over medium heat. Whisk in flour and cook for 30 seconds, stirring constantly. Gradually add milk and vegetable broth, whisking continuously to prevent lumps. Cook for 2-3 minutes until sauce thickens enough to coat the back of a spoon. Stir in salt, pepper, and ¼ cup shredded cheddar cheese until smooth.

Pour sauce over the carrot mixture in the baking dish.

In a small bowl, toss panko breadcrumbs with remaining 1 tablespoon olive oil until evenly coated. Stir in remaining ¼ cup shredded cheddar cheese. Spread topping evenly over the casserole.

Bake for 10-15 minutes until sauce is bubbly and topping is golden brown.