The best source for recipes is a book written in 1984 by Bess Cleveland, entitled "California Mission Recipes". It is available in most libraries and in used book stores for under $10.00. There are also two pages of recipes near the back of the Sunset publication The California Missions.
The food eaten at the mission was 'substantial', formed around grain and cornmeal, sharpened with chilies. Some of the specific dishes for which recipes have been found are Puchero (a broiled pot of beef and veal mixed with corn, potatoes, beans, onions, peppers, string beans, squash along with an apple and a pear), Posole (another mixed stew cooked in a large kettle) Torrejas (corn dough fritters), Tortillas and a dish called Relleno de Carne (chopped beef mixed with onions, raisins, black olives and an egg).
They also had recipes for sweets. One was called Dulce de Calabaz (a candied pumpkin), another was called a Jiricalla (a custard). The Spanish liked a thick chocolate called a Champurrado (it was thicker and sweeter than the Hot Chocolate we known today). Many of the missions had large groves of fruit trees so apples and pears were plentiful at some missions.
The Spanish preferred items made of wheat and would not eat corn, which they felt was beneath them
Some time ago the California Mission Studies Association published a recipe for Posole:
INGREDIENTS FOR POSOLE
1 onion, chopped;
2 cloves garlic, peeled and chopped;
2 tablespoon vegetable oil or lard;
1/2 teaspoon each black pepper, ground
cumin, cloves, cayenne;
1-1/2 lbs. pork shoulder, cooked and cut into 1-inch cubes;
2 to 3 cups canned white or yellow hominy (drained and rinsed);
3 to 5 cups pork broth, degreased and strained; 1 C canned chopped green chiles;
2 whole Jalapenos, canned or fresh (omit for milder recipe);
salt to taste.
In a large soup pot or kettle. Sauté the onion and garlic in oil or lard until wilted and beginning to brown. Add the spices, stirring to blend. Add the pork, drained and rinsed hominy, pork broth, the green chiles and jalapenos. Cook at a simmer, covered, for 45 to 60 minutes or until the meat and hominy are tender and the chiles and onions are well amalgamated into the broth. To assure a generous amount of broth for each serving of posole, add more water or broth as needed to keep pork covered in the final minutes of stewing. Remove posole from heat and cool slightly. Degrease the stew. Check to see if salt is needed. Reheat before serving. Ladle posole into wide soup plates and garnish (red or green salsa, finely shredded lettuce or cabbage, thinly sliced radishes, chunks of ripe avocado, chopped tomato and lime wedges). Warm flour tortillas and salsa are good accompaniments.