1kg of those mushrooms would be like 200 calories lol they're like 20cals per 100 grams but her recipe is off anyways because 100g of panko crumbs are around 390 calories (she used 120 so that's already more than 400), an egg 60-77 calories depending on size, 50g flour around 180cals. Light mayonnaise around 250-270 per 100g and the puree around 30cal per teaspoon assuming she's not generous lol, so add another 75 cals to everything. Obviously you wouldn't use every last bit but flat out writing 400 calories shows what an incompetent fraud she is. They seem generously coated enough so there wouldn't be loads of leftovers from coating them, I'd say they're closer to 600-700 than 400 calories. Tempted to check out the recipes in her book now not that I'd ever pay a cent for it. Wouldn't be that hard to give an actual count in MFP, log everything you use and deduct what's leftover and show the screenshot. She has no clue and she's lazy. That recipe is also not weightloss friendly at all, you'd be starving 30min later after consuming a ton of empty carb calories and less than 6g of protein and it is way too high in calories for a snack or appetiser.
Edit: There is also no need for flour when you're trying to cook light and are already using panko breadcrumbs. She has no clue and she's a danger to other women trying to lose weight.