Bring the water and a pinch of salt to a gentle boil in a heavy-bottomed pot over medium heat, watching as bubbles form and steam rises.
Slowly pour in the stone-ground grits while stirring constantly with a wooden spoon to prevent lumps, then reduce the heat to low and partially cover.
Let the grits simmer gently, stirring every 5 minutes, until they become thick, creamy, and slightly nutty in aroma, about 20-25 minutes.
While the grits cook, chop the onion and mince the garlic. Slice the sausage into thin rounds.
In a large skillet, melt 1 tablespoon of butter over medium heat until it starts to sizzle, then add the chopped onion and sauté until translucent and fragrant, about 3 minutes.
Add the minced garlic and cook for another 30 seconds until it releases a warm, savory aroma.
Toss in the sliced sausage and cook until it turns golden and smoky, about 4-5 minutes, stirring occasionally.
Push the sausage and vegetables to one side of the pan, then add the shrimp in a single layer. Sear over high heat until they turn bright pink and opaque, about 2 minutes per side, with a slight sizzle and aroma of freshness.
Stir in the Old Bay seasoning and cook for another minute to infuse the flavors into the shrimp and sausage.
Once the grits are creamy and thick, stir in the remaining butter and heavy cream until melted and blended, then taste and adjust with salt, pepper, or hot sauce for spice.
Remove the shrimp from the skillet and set aside. Squeeze fresh lemon juice over the shrimp and give everything a gentle stir to brighten the flavors.
Plate the creamy grits in bowls, then top generously with the smoky shrimp and sausage mixture. Drizzle with hot sauce or additional lemon juice if desired, and serve immediately while everything is hot and fragrant.
