Roast the poblano peppers whole using your preferred method - you can char them over a gas flame (either grill or stovetop, taking care holding the peppers with tongs). Alternatively, place them on a baking sheet/tray and roast in the oven at 400F/200C or under the broiler/overhead grill. In all cases, turn the peppers regularly so that the skin blisters and blackens evenly. Cooking time will vary depending on cooking method and size of peppers, so keep a close eye on them.

Once the peppers are well softened and have patches of black all over, remove from the heat. Place them in a plastic bag and fold over the top so that you create a steam packet. (Alternatively, you can place peppers on a plate and cover with cling wrap/cling film but a bag is less wasteful as you can wash and re-use after). Leave the peppers to steam and cool for around 10 minutes.

Remove the peppers from the bag, then peel off the skin - you can use a knife to get it started but your fingers are often easiest to do the peeling. Open up the pepper and remove the core and seeds. Don't worry if the pepper breaks up, strips are fine. At this point, you can store the roasted peppers in the fridge to make the sauce later, if you prefer.

Place the peppers, cilantro, Mexican crema, garlic and stock/bouillon powder in a food processor or blender. Blend everything together until well broken up and mixed.

Cook your pasta until al dente (just tender). When it is almost ready, warm the butter over a medium-low heat in a skillet/frying pan or saute pan large enough to hold the pasta, then add the sauce. Cook, stirring regularly, to warm through and thicken slightly.

When the pasta is ready, add it directly into the sauce and toss to coat the pasta all over. If it is too thick, add a little of the pasta cooking water.

Serve, topped with a sprinkling of cotija or queso fresco cheese (and some additional cilantro to garnish, if you like).