Heat the butter in a pan and cook the flour until it starts to get slightly brown in color.
Now add the garlic powder, ginger powder and onion powder and all the other ingredients and let it cook on low heat for a couple of additional minutes.
Take this off heat, and allow it to cool down completely. Now add the honey and give it a good mix.
Transfer this to a container lined with parchment paper and allow this to set in the refrigerator for 3-4 hours.
Notes
Use a good-quality gluten-free all-purpose flour blend to make sure the roux thickens properly without becoming grainy.
Cook the flour in melted butter until it turns lightly golden, stirring continuously to prevent it from burning.
Keep the heat low when adding the spices, as they can burn quickly and develop a bitter flavor.
If the mixture looks lumpy or too dry, add a little more butter and stir until it comes together.
Add the honey only after removing the mixture from the heat and allowing it to cool completely.
For a dairy-free version, replace the butter with olive oil or a suitable plant-based butter.
Add a pinch of cayenne pepper or chili powder if you prefer a spicier Japanese curry.
Transfer the roux to a parchment-lined container and refrigerate for 3–4 hours until firm before cutting it into portions.
Stir a portion of the roux into a simmering curry with vegetables, chicken, tofu, or paneer, adding water or stock as needed to achieve your desired consistency.