The basket occasionally went in the dishwasher which cleaned the surface, but the well gunked grease has been building up.
Tried soaking the basket in soap and hot water. Scrubbing with a soft sponge. And then running the dishwasher multiple times but it only got a small part of the grease out.
Post a picture of it, the basket and the mesh.
If it’s really bad then like someone else suggested: get some oven degreaser from the store, spray it down, let it sit for 10 minutes and wash off with hot water. Try not to breath the stuff, it’s nasty.
But you should be cleaning it weekly. Warm it up for a minute or two, then with folded paper towels wipe it out over a trash can. Leaving a light coating is actually to your advantage, it will keep the new stuff from sticking.