thanks for your replies. I adapted (more or less...) the following recipe which I found online:
Peruvian Recipes « Fighting Windmills
I didn't have aji panca or amarillo, so I used a strong red chilly pepper and a normal red pepper. I also used a large white onion, and beef stock (cube! shame on me) instead of plain water. For the slow cooker, I fried the onion, then put the fried onion plus meat plus mix plus some potatoes and sliced carrots (vegs at the bottom, peas on top - you could add the peas at the end though) and cooked on low for 8 hours, 6 was probably enough.
Seco de Res
2 lbs (bottom round) beef*
1 chopped red (or yellow) onion
2 Tbsp minced garlic
1 bunch fresh cilantro
1 cup frozen peas
1 Tbsp ají panca
1 Tbsp ají amarillo
vegetable (or olive) oil
salt, pepper, cumin powder to taste
*Try to buy a cut of quality bottom round with a little marbling for tenderness. We had good luck with meat from Costco. This method of cooking is called braising.
Cut the beef into hunks and season with salt, pepper, cumin powder, and minced garlic (I use the paste). Heat a little vegetable (or olive) oil in a stainless steel soup pot and pan fry the meat. When the meat is seared, add the chopped onion, ají panca, and ají amarillo. Stir until onion becomes translucent.
Rinse the cilantro in water and cut off the bottom few inches from the stems. Chop by hand and transfer to blender. Add about 1/2 to 1 cup water to the blender and reduce the fresh chopped cilantro to liquid.
Add liquid cilantro to soup pot, stir, lower heat and cover with lid. The meat will become tender, cooking in the liquid for at least 20 minutes. Add frozen peas, stir and cook covered another 10 minutes. Serve with white rice.