There are few words to describe this. We are forever indebted to you Nigella!!!
1 cup (packed) grated Gruyere cheese
2 tbs. grated Parmesan cheese
1 1/2 tbs. all-purpose flour
1/4 tsp. ground mace
1/4 tsp. sweet paprika
1/8 tsp. Aleppo pepper or hot paprika, plus more to sprinkle
250 whole milk
1 tsp. tomato paste
2 tbs. butter
1 fat clove garlic, grated
1/2 tsp. Worcestershire sauce
7 oz. conchigilie rigate pasta (or other large shell shape)
100g mixed white and dark crab
Stir together the cheese and set aside. Stir together the flour and spices and set aside. Pour the milk into a jug and stir in the tomato paste, then set aside.
Melt the butter in a smallish, heavy-based saucepan over a lowish heat. Stir in the garlic, then whisk in the flour mixture to make a foaming, orange paste. Take off the heat and gradually whisk in the tomatoey milk until completely smooth. Put back on the heat and cook for 3-5 minutes, then add the Worcestershire sauce. Take off the heat and stir in the cheeses. Cover and leave until the pasta is ready.
Cook the pasta according to package directions in boiling, salted water. Using a spider, ladle the pasta into the sauce and stir to combine. Fold in the crab and serve sprinkled with more Aleppo pepper or hot paprika.