Heat a saucepan over medium heat and add the butter. Stir in the garlic. Add the salt and pepper. Cook for just about 60 seconds. Slowly stream in 1 cup of the half and half, whisking the entire time. In a bowl, whisk together the remaining 1/2 cup half and half and cornstarch until no lumps remain to create a slurry. Stir the slurry into the saucepan and cook for a minute until the milk thickens. Reduce the heat to low.
Stir in the grated cheese, one small handful at a time, until melted.
Heat a large skillet over medium heat and add the chorizo, breaking it apart with a wooden spoon. Cook, stirring often and crumbling the chorizo apart, until it's browned, about 6 to 8 minutes.
In a bowl, stir together the onion, cilantro and lime juice with a pinch of salt.
To build the tacos, spread a few tablespoons of the queso on the flour tortilla. Wrap it around one of the hard shell tortillas. Fill the hard shell with the crumbled chorizo. Top with the onion and cilantro mixer. Repeat with remaining ingredients and serve with the extra queso!