In this tutorial, we learn how to make tarragon walnut brown butter sauce. You will need: 3 tbsp unsalted butter, 1/4 c freshly squeezed lemon juice, 1 tbsp chopped fresh tarragon, 2 tbsp chopped walnuts, salt and pepper. First, throw the chunk of butter into a sautee pan on medium heat until it foams up. Cook this for about 6-10 minutes until it turns a light brown color, then add in the walnuts. Be careful not to burn your walnuts, just swish around in the butter for 1 minute. After this, cool down the sauce with your fresh lemon juice and turn off the heat as soon as the mixture comes to a boil. Then add in your tarragon, salt and pepper. Spoon this over hot fish as soon as it's ready and it tastes great when prepared!