Preheat the oven to 375°F. Cook the pasta shells in salted boiling water for 2 minutes less than the package directions, then drain.
Whisk together all the ranch drizzle ingredients in a small bowl and chill until serving.
Melt the dairy free butter in a large pot over medium heat and cook the garlic for 1 minute. Add the dairy free cream cheese and oat milk and whisk until smooth.
Stir in the hot sauce, onion powder and dill, then add 1 cup of the cheddar shreds and stir until melted and creamy.
Fold in the chicken and pasta shells, then transfer to a 9x13 inch baking dish. Sprinkle with the remaining cheddar and bake for 20 minutes until hot and bubbly.
Drizzle with the ranch and top with green onions before serving.