• Before You Start: I highly encourage you to weigh your flour and butter using a kitchen scale. For weights, click the Metric button above. If you don't have a scale, here's how to measure flour with a measuring cup: Fluff the flour with a spoon, sprinkle it into the measuring cup, and level it off. Otherwise, you may scoop more than you need.
• Gather all the ingredients.
  

To Make a Brown Roux

• In a small saucepan, melt 3.5 oz unsalted butter over low to medium-low heat (you can cut the butter into small pieces first).
  
• When the butter is completely melted, add 3.5 oz all-purpose flour (plain flour). With a blunt-end wooden spatula, stir to combine the butter and flour.
  
• Soon, the butter and flour will fuse and swell. Cook for 20–25 minutes over low heat. Stir constantly because the roux burns easily. If the roux starts separating, switch to a whisk and mix vigorously.
  
• The roux will turn golden brown. You can even go for a bit darker color (watch my video).
  

To Make the Curry Roux

• Add 4 Tbsp Japanese curry powder, 1 Tbsp garam masala, and ½ tsp cayenne pepper (optional) to the roux. Tip: If you can‘t find garam masala, you can add more curry powder or (individual garam masala spices) in its place.
  
• Cook and stir for 30 seconds and remove from the heat. You can use the roux immediately (see the instructions below) or mold it into a block.
  

To Mold into a Block (overnight)

• Transfer the roux to a glass or metal container lined with parchment paper. Let it cool completely on the kitchen counter, then refrigerate to solidify overnight.
  
• The next day, take out the curry block from the container. If the curry block gets stuck to the container, release it with a butter knife or an offset spatula.
  
• With a sharp knife, cut the block into 8 cubes, about 1 x 1 inch (2.5 x 2.5 cm) each. Transfer the curry roux squares to a glass container.
  

To Store

• Store in the refrigerator for 1 month or in the freezer for 3–4 months. Use them soon for the best flavor and aroma.
  

To Use in a Curry Recipe

• Very important! Please season your final dish with more salt, as the homemade roux is unsalted. I usually add 2–4 tsp salt per block to the broth of my curry sauce recipe. Store-bought curry roux is quite salty, so you may want to add more salt to achieve a similar taste.
• Add the roux cubes or curry roux mixture (before it solidifies) to the broth of your curry recipe. Follow the recipe instructions on when to add it. Try it in recipes like my Chicken Curry, Instant Pot Curry, Vegetarian Curry, Beef Curry, Keema Curry, and Curry Udon.
• How much roux should we use? Roughly 6–7 cubes of this recipe are equivalent to one box of store-bought curry roux (that requires 4 cups or 1L of broth/water). Simmer over low heat for 5–10 minutes. Heat will thicken the roux.
• If the curry flavor is lacking or the curry does not thicken, add more roux. When you add meat and/or veggies, they release more moisture to the broth; therefore, you will need to adjust the amount of roux you use according to what you’re cooking.