01 -
Fire up your oven to 400°F before you start assembling your Wellington.
02 -
Rub your beef tenderloin all over with plenty of salt and pepper.
03 -
Pour olive oil into a big pan over high heat and brown the beef on every side until it's got a nice crust, roughly 2 to 3 minutes per side.
04 -
Take the beef off the heat and let it sit for a bit. When it's not hot anymore, smear mustard all over it.
05 -
Cut your mushrooms into tiny bits - a food processor makes this super easy.
06 -
Using the same pan, cook those mushroom bits on medium-high until they're dry and all the water's gone, about 10 to 15 minutes.
07 -
Lay down a big sheet of plastic wrap. Put the ham slices on it and spread your cooked mushrooms across the ham.
08 -
Put your mustard-covered beef in the middle and roll everything tight around it, using the plastic wrap to help. Twist the ends closed like a candy wrapper. Stick it in the fridge for 20 minutes.
09 -
Roll your puff pastry on a slightly floured counter until it's big enough to wrap around your beef bundle.
10 -
Take the beef out of the plastic and put it in the middle of your pastry. Brush beaten egg on the pastry edges. Fold the pastry over the beef, cut off any extra bits, and press it closed.
11 -
Put your wrapped beef on a baking sheet with the seam facing down. Brush more egg all over the top.
12 -
Make some shallow cuts on the pastry with a sharp knife, then sprinkle some chunky salt on top.
13 -
Stick it in your hot oven for 25 to 35 minutes until the crust turns golden and the meat inside reads 125°F to 130°F for a nice pink middle.
14 -
Pull it out and don't touch it for 10 minutes. Then cut into thick 1-inch slices.
15 -
Any leftovers can go in the fridge for up to 2 days. Warm them up in a 350°F oven.