Asparagus with mousseline sauce and catfish

The asparagus are very well this season, so I thought I could do another one. This time I chose a combination with fish and mashed potatoes. Ingredi├źnts: –┬á1 kg of asparagus – 1 dl of white wine – 1 onion – 1 teaspoon peppercorns – 2 egg yolks – 200 grams of butter – 600…