Heat a large saute pan to medium heat. Add the butter and let it melt then add the flour and stir to combine to make the roux. Let the roux cook for a couple of minutes then add in the curry powder and garam masala and mix well.
Slowly add the water to the roux a half cup at a time stirring quickly to dissolve the roux into the water.
Add the chicken, carrots, onions and potatoes and salt to the curry and season well with fresh ground pepper.
Cover and cook for 20 minutes or until the potatoes are fork tender.
While the curry cooks cook your rice according to package directions.