Put the Brussels sprouts and red onion into a microwaveable bowl with 1 tablespoon of water. Cover and zap on high for 3 minutes.
Meanwhile heat a frying pan over a medium to high heat. Drizzle in a little olive oil, add the chipolatas. Cook for about 7 minutes, turning regularly with tongs. Once cooked, turn down the heat to low and keep warm.
Melt most of the butter in a second non-stick frying pan over a medium to high heat. When bubbling, carefully uncover the microwaved sprouts and onion and tip into the pan. Season with a little salt and pepper, fry for 5 minutes until all the water has evaporated and the sprouts are starting to crisp.
Dump the lentils into the sprout pan. Crush in the garlic clove, strip the leaves off the thyme sprig. Add the final bit of butter and crank up the heat. Mix everything together, cook for 1-2 minutes until the lentils are warmed through, then stir in the mustard and balsamic vinegar.
Once the balsamic has bubbled off, season the lentils to taste then spoon into a bowl and pile the cooked chipolatas on top.
Swap the chipolatas for ready-cooked beetroot, cut into wedges and fried in a little olive oil for 2-3 minutes until warmed through.
About the chef
Joe Wicks, aka The Body Coach, is Britain's favourite healthy cook and fitness sensation – and a national treasure. His lockdown smash-hit 'PE With Joe' YouTube videos have been viewed 80 million times. He is the author of Lean in 15 - The Shift Plan, Lean in 15 - The Shape Plan, Lean in 15 - The Sustain Plan, The Fat-Loss Plan, Cooking for Family and Friends, Joe's 30-Minute Meals, Veggie Lean in 15, Wean in 15 and 30 Day Kick Start Plan.