Preheat oven to 375F. Add cooked and cooled rice to a large bowl. Chop thawed broccoli into small pieces. Add to bowl with rice.
Heat 2 tbsp. butter in a pan over medium high heat. Add onions. Sauté for 5 minutes. Add minced garlic and sauté for an additional minute. Transfer to bowl with rice and broccoli.
Lower to medium heat. Add the remaining 2 tbsp of butter. Allow it to melt, then add flour, whisking continuously for about one minute. Slowly add in milk, whisking continuously, until sauce thickens, for about two minutes. Then add in velveeta cubes. Stir until velveeta is fully melted and incorporated. Remove from heat.
Combine cooked rice, broccoli, sour cream, half of shredded cheddar cheese, salt and pepper and cheese sauce mixture. Mix well.
Pour into a greased 8.5x12 casserole dish, top with remaining cheese and sprinkle the Panko crumbs over top.
Bake for 25 to 30 minutes, until top is golden brown. Garnish with chopped green onions before serving if desired.
Any variety of rice will work. Try out basmati, jasmine, or brown rice for some fun flavors. Go ahead and make the rice the morning of to save you time when you are ready to make the recipe. If you decide to use fresh broccoli, chop into small pieces and follow the rest of the directions.