package com.example.examplemod;

import net.minecraftforge.registries.ForgeRegistries;

import java.rmi.registry.Registry;
import net.minecraft.core.registries.BuiltInRegistries;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.world.effect.MobEffectInstance;
import net.minecraft.world.effect.MobEffects;
import net.minecraft.world.item.Items;
import net.minecraft.world.item.alchemy.Potion;
import net.minecraft.world.item.alchemy.Potions;

public class CustomPotion{
	
	public static final Potion witherPotion =
	        Registry.register(Registry.POTION, new Identifier("tutorial", "Witherpotion"),
	            new Potion(new MobEffectInstance(MobEffects.WITHER, 3600, 1)));
	 
	    public static void registerPotions(){
	    	
	    }
	 
	    public static void registerPotionsRecipes(){
	        BrewingRecipeRegistryMixin.invokeRegisterPotionRecipe(Potions.AWKWARD, Items.WITHER_ROSE, CustomPotion.witherPotion);
	    }
}

The errors are:
POTION cannot be resolved or is not a field    CustomPotion.java   
Identifier cannot be resolved to a type    CustomPotion.java
 

The problem with potion identification and registration may be caused by incorrect use of the Registry class and the undefined new identifier() method. To register a potion, use the register method of the ForgeRegistries.POTION class instead of Registry.POTION. Make sure you have defined the Registry correctly and imported the required classes. Additionally, you are missing a method definition for invokeRegisterPotionRecipe().