- Into a large, deep skillet over medium-high heat, add the butter and vegetable oil. 
- When the butter is melted, add mixed mushrooms. Cook for 1 minute. 
- Add sea salt, ground black pepper, cayenne pepper, and nutmeg. Cook, stirring frequently, 2 more minutes. 
- Sprinkle with all-purpose flour then gradually add chicken-style broth ¼ cup at a time, whisking after each addition. 
- Bring just to a simmer then reduce heat to low. 
- Add sour cream, unsweetened almond milk, and butter. Whisk until thoroughly combined and butter is melted. 
- Continue cooking, stirring frequently, for about 5 minutes, until sauce is thickened.