Heat your oven to 220°C/Fan 200°C/Gas 7. Pat the pork dry with kitchen paper. Peel and grate 1 garlic clove. Put in a bowl. Squeeze in the mustard. Whisk with ½ tbsp oil and some salt and pepper.
Finely chop the rosemary leaves. Rub the Dijon mix all over the pork. Press the rosemary on to the pork. Lay it in a baking dish lined with baking paper. Nestle in the tomatoes and remaining garlic clove. Roast for 15 mins.
While the pork is cooking, pull the broad beans from their pods. Tip the beans into a pan of boiling water and cook for 2 mins. Drain, then plunge the beans into ice cold water. Pop them from their grey skins if you like. Finely chop the mint leaves. Zest the lemon. Drain and rinse the cannellini beans.
After the pork has cooked for 15 mins, take it out of the oven. Pluck out the garlic clove. Turn the oven down to 180°C/Fan 160°C/Gas 4. Roast for a further 10 mins. Pierce the thickest part of the pork and the juices should be clear. If not, cook a little longer till they do. Remove the pork from the oven and cover with foil. Leave to rest for 10 mins.
Meanwhile, tip the cannellini beans into a pan. Squeeze in the flesh from the roasted garlic clove. Add 1 tbsp oil and 2 tbsp water and place on a medium heat. Warm through for 3 mins. Add the broad beans to the pan. Cook for a further 2 mins.
Remove the pan from the heat. Blitz the beans to a smooth purée with a hand-held blender or in a food processor. Or, crush with a masher. It won’t be as smooth but just as delicious (mashing will be easier if you removed the broad bean skins).
Add the lemon zest and mint to the purée and stir together. Taste and season. Squeeze in a little lemon juice if you like.
Whisk the juice from half the lemon with ½ tbsp oil. Toss through the salad leaves. Slice the pork. Spoon the purée onto 2 plates and top with the pork slices. Serve with the roast tomatoes and salad.