Preheat oven to 220°C fan bake or 230°C conventional bake.
Heat butter in a pan over a medium-low heat.
Add the mushrooms, rosemary, shallots and garlic.
Cook, stirring frequently for 20 minutes until everything is very soft and all the liquid has evaporated.
Stir through the mustard and season with a little salt and pepper to taste.
Meanwhile, heat a little oil in a frying pan over a very high heat.
Trim the lamb rumps of any fat, pat dry with paper towels and season with salt and pepper.
Add to the pan (2 at a time) to brown slightly on all sides – only about 30 seconds in the pan in total. Set aside on a wooden board and repeat with the other rumps.
Roll out the pastry on a floured benchtop – it needs to be about ¾ the thickness of a standard sheet, about 2-3 mm.
If the pastry is too thick, it won’t cook properly by the time the lamb rump is ready.
Press some of the mushroom mixture in a layer around the outside of a lamb rump. Gently place the lamb on a piece of pastry.
Brush all the pastry edges with egg mixture and press the ends firmly together to seal.
Place the roll seam-side down on a baking tray lined with baking paper.
Brush all over with egg wash, then using a sharp knife, score a series of light cuts in a crisscross all over the top.
Bake in the oven for 12 minutes, then remove the tray from the oven and allow to rest for 8-10 minutes before slicing.

MAKE THE SALAD
In a bowl, mix salad ingredients together with the dressing and season with salt and pepper.

MAKE THE VINAIGRETTE
In a small jug whisk olive oil, vinegar and mustard. Drizzle over salad.

TO SERVE
Slice the Wellingtons in halves, thirds or serve whole and arrange on plates with the salad.

Recipe from recipes.co.nz