In a small pot, combine the white wine, vinegar and shallots. Put on medium-high heat and reduce to about 1 tbsp. Set aside for later.
In a small pot, melt the butter and then add the flour. Let cook for 1-2 minutes until it smells nutty and it looks like wet sand. Now add the milk and bring to a simmer to thicken. Turn down the heat to low and add the shredded gruyere. Once the cheese is incorporated, thin the sauce with the white wine-shallot reduction. Adjust consistency with milk and season with salt and pepper.
Place the cauliflower steamer into the microwave and cook for 5-8 minutes until tender.
Carefully remove the vegetables from the steamer package and drizzle the warm cheese sauce. Enjoy with a pinot gris!