Q.I have mushroom fungi in my growing box this year when I uncovered it, can I still grow my lettuce in it if I scrape it out?
Compost planter has been covered during wet weather to stop it becoming water logged, when I uncovered it to plant lettuce it has a yellow web like fungi growing in it, can I still grow lettuce , is it safe to use the compost if I remove the fungi?

Certified GKH Gardening Expert
Those are Peziza and are very beneficial to breaking down soil and making it into nutrients for plants. To be sure that they don't find your plant roots a suitable snack, you should recompost the soil. Correct composting temperatures will kill off the fungus, while making the fruit bodies break down into usable nutrients for your plants. Although, using the soil won't really harm much as it is.
Picking off the fruiting bodies will be fine, but that is just a small portion of the actual mushroom. The rest is living inside the soil, throughout its entirety.
This article will help you to compost the soil to make it as nutrient rich as possible for your plants: https://www.gardeningknowhow.com/composting/basics/ultimate-beginners-guide-composting.htm