Cook linguine as directed on package and set aside
In a large preheated pot, add in the cooking oil. Add in the shrimp paste and saute until fragrant about 1 minutes. Add in the paste you grind earlier, the lemongrass stalks and saute until really fragrant, about 5 minutes. Add in the chicken pieces and cook until they turn color. Pour in the chicken stock and sugar. Bring to a boil and then lower the heat to let the chicken cooked through, about 15 minutes or so. Add in the mushrooms and let it cook for another 5 minutes
Add in the coconut milk and bring it back to a boil. As soon as it boils, turn off the heat to avoid the coconut milk turn foamy from overcooking. Have a taste. It should be savory and just a hint of sweetness. Add more salt if needed
Portion the cooked linguine into serving platter or bowl. Spoon some of the chicken and mushrooms on top of the noodles and then generously spoon the broth over the noodles. Garnish with some fried shallots crisp, cilantro leaves, and slices of red chilis if you want. Serve immediately