Step 1
Melt butter in a large heavy saucepan over low heat. Add onion and cook until tender. Stir in flour; cook and stir until smooth about 1 minute. Reduce heat if mixture browns too quickly.
Step 2
Gradually add 1/2 cup of chicken broth and cook over medium heat stirring constantly until thickened and bubbly. Stir in dry mustard salt and chopped chicken; whisk in egg yolks.
Step 3
Cook over medium heat stirring constantly for 4 to 5 minutes. Remove from heat. Refrigerate 3 to 4 hours or preferably overnight.
Step 4
Combine remaining 1/4 cup chicken broth and hot pepper paste; stir into chilled chicken mixture.
Step 5
Shape chicken mixture into patties (an ice cream scoop will give you consistent size patties). Dredge patties in cracker crumbs.
Step 6
Pour 1/2 inch oil into skillet. Heat to 375 degrees F (190 degrees C) over medium-high heat. When oil is hot fry the croquettes until golden brown; do not turn the croquettes until they are well browned on the first side 4 to 5 minutes. Turn and cook the other side 4 to 5 minutes. Fry in batches as needed. Drain on paper towels.
Step 7
Melt 1/3 cup butter in a skillet over medium high heat. Add garlic and cook for 30 seconds to 1 minute stirring constantly to prevent it from burning. Stir in flour and whisk continuously for 1 minute.
Step 8
Pour in the milk and herbs and continue to cook whisking constantly until sauce begins to thicken about 1 minute. Ladle sauce over croquettes on serving plates.