Preheat the grill to a medium temperature.

Add the mushrooms and poblanos, and brush them with a little olive oil.

While the vegetables are cooking, prepare the avocado crema. Combine the avocado, sour cream, cilantro, lime juice, salt and pepper in a food processor. Blend until smooth, then check for seasoning and add more if required. Transfer to a serving bowl, cover, and keep in the fridge until required. 

Turn the veggies half way through cooking. When the vegetables are cooked, remove from the grill.

Slice the mushrooms. Remove the majority of the blackened skin from the poblanos, remove the stem and seeds, then slice.

Warm some low carb tortillas (they only need a few seconds in the microwave or a minute on the grill), and then load them up with the mushrooms and poblanos. Finish with a few spoonfuls of avocado crema and some fresh cilantro leaves.