(To prepare the night before)
1. Melt rendered chicken fat gently in a small skillet.
2. Whisk eggs in a small bowl.  Slowly add chicken fat while whisking.
3. To the bowl, add salt and pepper, then parsley and sage, whisking to incorporate.
4. Add mushrooms and mix.
5. Slowly add matzo meal while mixing.
6. Stir in club soda.
7. Chill mixture in refrigerator, covered, for several hours or overnight.

(To finish the recipe)
1. Bring chicken broth to a boil in a large stock pot. Add vegetables.

2. With damp hands, form cold matzo mixture into 1-inch balls.

3. Drop matzo balls into boiling water.

4. Reduce heat to low, cover and allow matzo balls to simmer 40 minutes, until tender.

5. To serve, ladle soup and matzo balls into bowls. Garnish with chopped fresh parsley.