Rinse the rice under cold water until the water runs clear to remove excess surface starch.
In a medium saucepan, melt butter over medium heat. Add diced onions and sauté for 3-4 minutes until translucent.
Add minced garlic and sauté for 1 minute until fragrant.
Stir in the rinsed rice and toast for 2 minutes, ensuring each grain is coated in butter.
Pour in the chicken broth and bring to a boil over high heat.
Reduce heat to low, cover with a tight-fitting lid, and simmer for 15-18 minutes or until liquid is fully absorbed.
Remove from heat and let rest, covered, for 5 minutes.
Remove lid and fluff the rice with a fork. Stir in the heavy cream over low heat.
Gradually fold in the cheddar and parmesan cheeses until completely melted and the texture is creamy.
Season with salt and pepper. Garnish with fresh parsley before serving.