1 Sift the cornmeal, flour, salt and baking powder.
Rub in the lard (shortening) until the mix- ture is like breadcrumbs.
2 Add some of the water with the egg, to form a stiff dough. Knead it for a few minutes and then let it rest for 1/2 hour.
3 Take pieces the size of a walnut, and roll out to 15 cm (6 in) circles, 3 mm (1/8 in) thick.
4 Preheat the oven to 200°C, 400°F,gas6.
5 Heat a heavy cast-iron griddle or frying pan (skillet), ungreased, until a drop of water sizzles on the surface.
Cook each tortilla for 1 minute on each side until brown flecks appear.
When cooked, keep warm in the oven, wrapped in foil.
6 To make the dip, mix the avocados, onion and lemon juice in an electric blender until smooth.
7 Beat the cream cheese until light and add to the avocado mix- ture.
Add the celery, chilli powder and salt.
8 Serve immediately as a dip for the tortillas.