1. Caramelize onions in half the oil, about 20 minutes, use water to deglaze hotspots.
2. Add remaining oil and butter and melt then add flour and stir constantly until flour turns a golden brown color.
3. Add curry powder, salt, sugar, and chicken base and stir until combined.
4. Begin adding in the water a gallon at a time to keep the mixture hot. Stir to combine after each gallon.
5. Bring to a simmer and add the carrots and potatoes. Simmer until you reach your desired consistency. You can use water or stock to thin and use a 1:1 corn starch to cold water slurry to thicken.