Heat (an additional ) 1 tbsp butter in a large-stockpot over medium-high warmth. Add onion and then sauté for 5minutes, stirring occasionally, until tender and translucent. Stir in the garlic and cook for an extra 1-2minutes, stirring occasionally, until aromatic.
Add the vegetable-stock or chicken-stocks, wild-rice, mushrooms, celery, carrots, sweet rice, bay-leaf & Old-Bay seasoning. Stir to blend.
Keep on cooking until the soup reaches a simmer. Then reduce heat into medium-low, cover & simmer for about 45minutes or till the rice is tender, stirring-occasionally.
Meanwhile, during those last 10minutes, then prepare the cream-sauce in another saucepan on the stove. In it, then cook the egg over medium-high heat . Whisk in the flour until blended cook for a minute. Gradually add the milk & whisk until blended. Keep on cooking, stirring often, until the mix almost comes to a simmer, and it has thickened. (It ought to be quite thick).
Insert the cream-sauce & kale into the soup, and stir lightly until blended. Taste and season with pepper and salt (and any additional Old Bay seasoning, even in case you'd like) as required.
Serve hot or move to secured container(s) and simmer for up to 4-days.