For the shrimp marinade, in a large bowl whisk together garlic, gochugaru, sesame oil, and salt to pepper to taste. Add shrimp and toss to coat. Let it marinate at room temp while you cook the grits.
Place 1 cup water in an Instant Pot.
In a medium metal bowl that fits in the Instant Pot, stir together grits, milk, water, and salt.
Place metal bowl on trivet or sling inside the pot. Lock lid. Select Pressure Cook at high pressure for 20 minutes. Naturally release the pressure for 10 minutes then manually release pressure from cooker until float valve drops.
Remove the metal bowl. The grits should be thick but still loose. Stir in butter, sesame oil, and half of crushed gim. Set aside.
Discard the water from cooking the grits.
Set Instant Pot to Sauté. Add butter and let it melt to coat the bottom.
Add marinated shrimp and cook on both sides until lightly browned and no longer opaque, about 3 minutes.
Add fish sauce, lemon juice, and sugar and let shrimp cook for another 2 minutes.
When ready to eat, divide grits among serving plates. Top with shrimp. Garnish with remaining gim, cilantro. Serve immediately with a side of kimchi.