Learn Dutch: Er blaffen twee honden op de stoep. - There are two dogs barking on the sidewalk.

In English, you usually say "There are [noun] [verb-ing]", like "There are two dogs barking." Dutch skips the "are" completely! Instead, it puts the action verb directly after the dummy subject er. Literally, it says "There bark two dogs on the sidewalk."

If Er is the first word, why is the verb blaffen in the plural form?

Even though er sits in the subject spot to introduce the sentence, the real subject doing the action is twee honden (two dogs). Because twee honden is plural, the verb must also be plural: blaffen.

Could I say Er blaffen de honden to mean "There are the dogs barking"?

No, you cannot use this er structure with a specific, definite subject like de honden (the dogs) or mijn honden (my dogs). Presentative er is only used to introduce new, indefinite things into a conversation. If you want to talk about specific dogs, you just make them the normal subject at the start: De honden blaffen op de stoep.

Is it wrong to just say Twee honden blaffen op de stoep without using er?