This is a traditional Mexican dish, in its basic version, with loads of melted cheese and chorizo sausage.
Heat oil in a medium pan.
Add salsa and broth and let simmer for 5 mins. Taste and adjust with salt and pepper.
Add a handful of corn chips into the sauce to cover them, with a slotted spoon remove the corn chips and serve on a plate.
Top the corn chips with sour cream, cheese, and slices of onion.
A tostada is a corn tortilla that has been fried to a perfect crunchiness, you can eat it just as is, or top it with different dishes and garnishes.